diff --git a/CHANGES.rst b/CHANGES.rst
index d7d1c88f..587b1bfd 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -9,6 +9,8 @@ Minor changes:
 - Added ``end``, ``start``, ``duration``, ``DTSTART``, ``DUE``, and ``DURATION`` attributes to ``Todo`` components. See `Issue 662`_.
 - Format test code with Ruff. See `Issue 672 <https://github.com/collective/icalendar/issues/672>`_.
 - Document the Debian package. See `Issue 701 <https://github.com/collective/icalendar/issues/701>`_.
+- Document ``vDatetime.from_ical``
+- Allow passing a ``datetime.date`` to ``TZP.localize_utc`` and ``TZP.localize`` methods.
 - Document component classes with description from :rfc:`5545`.
 
 Breaking changes:
@@ -19,6 +21,13 @@ New features:
 
 - Add ``VALARM`` properties for :rfc:`9074`. See `Issue 657 <https://github.com/collective/icalendar/issues/657>`_
 - Test compatibility with Python 3.13
+- Add ``icalendar.alarms`` module to calculate alarm times. See `Issue 716 <https://github.com/collective/icalendar/issues/716>`_.
+- Add ``Event.alarms`` and ``Todo.alarms`` to access alarm calculation.
+- Add ``Component.DTSTAMP`` and ``Component.LAST_MODIFIED`` properties for datetime in UTC.
+- Add ``Component.is_thunderbird()`` to check if the component uses custom properties by Thunderbird.
+- Add ``X_MOZ_SNOOZE_TIME`` and ``X_MOZ_LASTACK`` properties to ``Event`` and ``Todo``.
+- Add ``Alarm.ACKNOWLEDGED``, ``Alarm.TRIGGER``, ``Alarm.REPEAT``, and ``Alarm.DURATION`` properties
+  as well as ``Alarm.triggers`` to calculate alarm triggers.
 
 Bug fixes:
 
diff --git a/docs/api.rst b/docs/api.rst
index 757f905c..ac211638 100644
--- a/docs/api.rst
+++ b/docs/api.rst
@@ -1,6 +1,13 @@
 API Reference
 -------------
 
+icalendar.alarms
+++++++++++++++++
+
+.. automodule:: icalendar.alarms
+   :members:
+
+
 icalendar.cal
 +++++++++++++
 
diff --git a/src/icalendar/__init__.py b/src/icalendar/__init__.py
index d0e5f10e..e1a09a02 100644
--- a/src/icalendar/__init__.py
+++ b/src/icalendar/__init__.py
@@ -1,3 +1,11 @@
+from icalendar.alarms import (
+    Alarms,
+    AlarmTime,
+    ComponentEndMissing,
+    ComponentStartMissing,
+    IncompleteAlarmInformation,
+    LocalTimezoneMissing,
+)
 from icalendar.cal import (
     Alarm,
     Calendar,
@@ -94,4 +102,10 @@
     "vMonth",
     "IncompleteComponent",
     "InvalidCalendar",
+    "Alarms",
+    "AlarmTime",
+    "ComponentEndMissing",
+    "ComponentStartMissing",
+    "IncompleteAlarmInformation",
+    "LocalTimezoneMissing",
 ]
diff --git a/src/icalendar/alarms.py b/src/icalendar/alarms.py
new file mode 100644
index 00000000..e8999d13
--- /dev/null
+++ b/src/icalendar/alarms.py
@@ -0,0 +1,388 @@
+"""Compute the times and states of alarms.
+
+This takes different calendar software into account and the RFC 9074 (Alarm Extension).
+
+- RFC 9074 defines an ACKNOWLEDGED property in the VALARM.
+- Outlook does not export VALARM information.
+- Google Calendar uses the DTSTAMP to acknowledge the alarms.
+- Thunderbird snoozes the alarms with a X-MOZ-SNOOZE-TIME attribute in the event.
+- Thunderbird acknowledges the alarms with a X-MOZ-LASTACK attribute in the event.
+- Etar deletes alarms that are acknowledged.
+- Nextcloud's Webinterface does not do anything with the alarms when the time passes.
+"""
+
+from __future__ import annotations
+
+from datetime import date, timedelta, tzinfo
+from typing import TYPE_CHECKING, Generator, Optional, Union
+
+from icalendar.cal import Alarm, Event, Todo
+from icalendar.timezone import tzp
+from icalendar.tools import is_date, normalize_pytz, to_datetime
+
+if TYPE_CHECKING:
+    from datetime import datetime
+
+Parent = Union[Event,Todo]
+
+
+class IncompleteAlarmInformation(ValueError):
+    """The alarms cannot be calculated yet because information is missing."""
+
+class ComponentStartMissing(IncompleteAlarmInformation):
+    """We are missing the start of a component that the alarm is for.
+
+    Use Alarms.set_start().
+    """
+
+class ComponentEndMissing(IncompleteAlarmInformation):
+    """We are missing the end of a component that the alarm is for.
+
+    Use Alarms.set_end().
+    """
+
+class LocalTimezoneMissing(IncompleteAlarmInformation):
+    """We are missing the local timezone to compute the value.
+
+    Use Alarms.set_local_timezone().
+    """
+
+
+class AlarmTime:
+    """An alarm time with all the information."""
+
+    def __init__(
+            self,
+            alarm: Alarm,
+            trigger : datetime,
+            acknowledged_until:Optional[datetime]=None,
+            snoozed_until:Optional[datetime]=None,
+            parent: Optional[Parent]=None,
+        ):
+        """Create a new AlarmTime.
+
+        alarm
+            the Alarm component
+
+        trigger
+            a date or datetime at which to trigger the alarm
+
+        acknowledged_until
+            an optional datetime in UTC until when all alarms
+            have been acknowledged
+
+        snoozed_until
+            an optional datetime in UTC until which all alarms of
+            the same parent are snoozed
+
+        parent
+            the optional parent component the alarm refers to
+
+        local_tzinfo
+            the local timezone that events without tzinfo should have
+        """
+        self._alarm = alarm
+        self._parent = parent
+        self._trigger = trigger
+        self._last_ack = acknowledged_until
+        self._snooze_until = snoozed_until
+
+    @property
+    def acknowledged(self) -> Optional[datetime]:
+        """The time in UTC at which this alarm was last acknowledged.
+
+        If the alarm was not acknowledged (dismissed), then this is None.
+        """
+        ack = self.alarm.ACKNOWLEDGED
+        if ack is None:
+            return self._last_ack
+        if self._last_ack is None:
+            return ack
+        return max(ack, self._last_ack)
+
+    @property
+    def alarm(self) -> Alarm:
+        """The alarm component."""
+        return self._alarm
+
+    @property
+    def parent(self) -> Optional[Parent]:
+        """This is the component that contains the alarm.
+
+        This is None if you did not use Alarms.set_component().
+        """
+        return self._parent
+
+    def is_active(self) -> bool:
+        """Whether this alarm is active (True) or acknowledged (False).
+
+        For example, in some calendar software, this is True until the user looks
+        at the alarm message and clicked the dismiss button.
+
+        Alarms can be in local time (without a timezone).
+        To calculate if the alarm really happened, we need it to be in a timezone.
+        If a timezone is required but not given, we throw an IncompleteAlarmInformation.
+        """
+        acknowledged = self.acknowledged
+        if not acknowledged:
+            # if nothing is acknowledged, this alarm counts
+            return True
+        if self._snooze_until is not None and self._snooze_until > acknowledged:
+            return True
+        trigger = self.trigger
+        if trigger.tzinfo is None:
+            raise LocalTimezoneMissing(
+                "A local timezone is required to check if the alarm is still active. "
+                "Use Alarms.set_local_timezone()."
+            )
+        return trigger > acknowledged
+
+    @property
+    def trigger(self) -> date:
+        """This is the time to trigger the alarm.
+
+        If the alarm has been snoozed, this can differ from the TRIGGER property.
+        """
+        if self._snooze_until is not None and self._snooze_until > self._trigger:
+            return self._snooze_until
+        return self._trigger
+
+
+class Alarms:
+    """Compute the times and states of alarms.
+
+    This is an example using RFC 9074.
+    One alarm is 30 minutes before the event and acknowledged.
+    Another alarm is 15 minutes before the event and still active.
+
+    >>> from icalendar import Event, Alarms
+    >>> event = Event.from_ical(
+    ... '''BEGIN:VEVENT
+    ... CREATED:20210301T151004Z
+    ... UID:AC67C078-CED3-4BF5-9726-832C3749F627
+    ... DTSTAMP:20210301T151004Z
+    ... DTSTART;TZID=America/New_York:20210302T103000
+    ... DTEND;TZID=America/New_York:20210302T113000
+    ... SUMMARY:Meeting
+    ... BEGIN:VALARM
+    ... UID:8297C37D-BA2D-4476-91AE-C1EAA364F8E1
+    ... TRIGGER:-PT30M
+    ... ACKNOWLEDGED:20210302T150004Z
+    ... DESCRIPTION:Event reminder
+    ... ACTION:DISPLAY
+    ... END:VALARM
+    ... BEGIN:VALARM
+    ... UID:8297C37D-BA2D-4476-91AE-C1EAA364F8E1
+    ... TRIGGER:-PT15M
+    ... DESCRIPTION:Event reminder
+    ... ACTION:DISPLAY
+    ... END:VALARM
+    ... END:VEVENT
+    ... ''')
+    >>> alarms = Alarms(event)
+    >>> len(alarms.times)   # all alarms including those acknowledged
+    2
+    >>> len(alarms.active)  # the alarms that are not acknowledged, yet
+    1
+    >>> alarms.active[0].trigger  # this alarm triggers 15 minutes before 10:30
+    datetime.datetime(2021, 3, 2, 10, 15, tzinfo=ZoneInfo(key='America/New_York'))
+
+    RFC 9074 specifies that alarms can also be triggered by proximity.
+    This is not implemented yet.
+    """
+
+    def __init__(self, component:Optional[Alarm|Event|Todo]=None):
+        """Start computing alarm times."""
+        self._absolute_alarms : list[Alarm] = []
+        self._start_alarms : list[Alarm] = []
+        self._end_alarms : list[Alarm] = []
+        self._start : Optional[date] = None
+        self._end : Optional[date] = None
+        self._parent : Optional[Parent] = None
+        self._last_ack : Optional[datetime] = None
+        self._snooze_until : Optional[datetime] = None
+        self._local_tzinfo : Optional[tzinfo] = None
+
+        if component is not None:
+            self.add_component(component)
+
+    def add_component(self, component:Alarm|Parent):
+        """Add a component.
+
+        If this is an alarm, it is added.
+        Events and Todos are added as a parent and all
+        their alarms are added, too.
+        """
+        if isinstance(component, (Event, Todo)):
+            self.set_parent(component)
+            self.set_start(component.start)
+            self.set_end(component.end)
+            if component.is_thunderbird():
+                self.acknowledge_until(component.X_MOZ_LASTACK)
+                self.snooze_until(component.X_MOZ_SNOOZE_TIME)
+            else:
+                self.acknowledge_until(component.DTSTAMP)
+
+        for alarm in component.walk("VALARM"):
+            self.add_alarm(alarm)
+
+    def set_parent(self, parent: Parent):
+        """Set the parent of all the alarms.
+
+        If you would like to collect alarms from a component, use add_component
+        """
+        if self._parent is not None and self._parent is not parent:
+            raise ValueError("You can only set one parent for this alarm calculation.")
+        self._parent = parent
+
+    def add_alarm(self, alarm: Alarm) -> None:
+        """Optional: Add an alarm component."""
+        trigger = alarm.TRIGGER
+        if trigger is None:
+            return
+        if isinstance(trigger, date):
+            self._absolute_alarms.append(alarm)
+        elif alarm.TRIGGER_RELATED == "START":
+            self._start_alarms.append(alarm)
+        else:
+            self._end_alarms.append(alarm)
+
+    def set_start(self, dt: Optional[date]):
+        """Set the start of the component.
+
+        If you have only absolute alarms, this is not required.
+        If you have alarms relative to the start of a compoment, set the start here.
+        """
+        self._start = dt
+
+    def set_end(self, dt: Optional[date]):
+        """Set the end of the component.
+
+        If you have only absolute alarms, this is not required.
+        If you have alarms relative to the end of a compoment, set the end here.
+        """
+        self._end = dt
+
+    def _add(self, dt: date, td:timedelta):
+        """Add a timedelta to a datetime."""
+        if is_date(dt):
+            if td.seconds == 0:
+                return dt + td
+            dt = to_datetime(dt)
+        return normalize_pytz(dt + td)
+
+    def acknowledge_until(self, dt: Optional[date]) -> None:
+        """This is the time in UTC when all the alarms of this component were acknowledged.
+
+        Only the last call counts.
+
+        Since RFC 9074 (Alarm Extension) was created later,
+        calendar implementations differ in how they acknowledge alarms.
+        For example, Thunderbird and Google Calendar store the last time
+        an event has been acknowledged because of an alarm.
+        All alarms that happen before this time count as acknowledged.
+        """
+        self._last_ack = tzp.localize_utc(dt) if dt is not None else None
+
+    def snooze_until(self, dt: Optional[date]) -> None:
+        """This is the time in UTC when all the alarms of this component were snoozed.
+
+        Only the last call counts.
+
+        The alarms are supposed to turn up again at dt when they are not acknowledged
+        but snoozed.
+        """
+        self._snooze_until = tzp.localize_utc(dt) if dt is not None else None
+
+    def set_local_timezone(self, tzinfo:Optional[tzinfo|str]):
+        """Set the local timezone.
+
+        Events are sometimes in local time.
+        In order to compute the exact time of the alarm, some
+        alarms without timezone are considered local.
+
+        Some computations work without setting this, others don't.
+        If they need this information, expect a LocalTimezoneMissing exception
+        somewhere down the line.
+        """
+        self._local_tzinfo = tzp.timezone(tzinfo) if isinstance(tzinfo, str) else tzinfo
+
+    @property
+    def times(self) -> list[AlarmTime]:
+        """Compute and return the times of the alarms given.
+
+        If the information for calculation is incomplete, this will raise a
+        IncompleteAlarmInformation exception.
+
+        Please make sure to set all the required parameters before calculating.
+        If you forget to set the acknowledged times, that is not problem.
+        """
+        return (
+            self._get_end_alarm_times() +
+            self._get_start_alarm_times() +
+            self._get_absolute_alarm_times()
+        )
+
+    def _repeat(self, first: datetime, alarm: Alarm) -> Generator[datetime]:
+        """The times when the alarm is triggered relative to start."""
+        yield first # we trigger at the start
+        repeat = alarm.REPEAT
+        duration = alarm.DURATION
+        if repeat and duration:
+            for i in range(1, repeat + 1):
+                yield self._add(first, duration * i)
+
+    def _alarm_time(self, alarm: Alarm, trigger:date):
+        """Create an alarm time with the additional attributes."""
+        if getattr(trigger, "tzinfo", None) is None and self._local_tzinfo is not None:
+            trigger = normalize_pytz(trigger.replace(tzinfo=self._local_tzinfo))
+        return AlarmTime(alarm, trigger, self._last_ack, self._snooze_until, self._parent)
+
+    def _get_absolute_alarm_times(self) -> list[AlarmTime]:
+        """Return a list of absolute alarm times."""
+        return [
+            self._alarm_time(alarm , trigger)
+            for alarm in self._absolute_alarms
+            for trigger in self._repeat(alarm.TRIGGER, alarm)
+        ]
+
+    def _get_start_alarm_times(self) -> list[AlarmTime]:
+        """Return a list of alarm times relative to the start of the component."""
+        if self._start is None and self._start_alarms:
+            raise ComponentStartMissing("Use Alarms.set_start because at least one alarm is relative to the start of a component.")
+        return [
+            self._alarm_time(alarm , trigger)
+            for alarm in self._start_alarms
+            for trigger in self._repeat(self._add(self._start, alarm.TRIGGER), alarm)
+        ]
+
+    def _get_end_alarm_times(self) -> list[AlarmTime]:
+        """Return a list of alarm times relative to the start of the component."""
+        if self._end is None and self._end_alarms:
+            raise ComponentEndMissing("Use Alarms.set_end because at least one alarm is relative to the end of a component.")
+        return [
+            self._alarm_time(alarm , trigger)
+            for alarm in self._end_alarms
+            for trigger in self._repeat(self._add(self._end, alarm.TRIGGER), alarm)
+        ]
+
+    @property
+    def active(self) -> list[AlarmTime]:
+        """The alarm times that are still active and not acknowledged.
+
+        This considers snoozed alarms.
+
+        Alarms can be in local time (without a timezone).
+        To calculate if the alarm really happened, we need it to be in a timezone.
+        If a timezone is required but not given, we throw an IncompleteAlarmInformation.
+        """
+        return [alarm_time for alarm_time in self.times if alarm_time.is_active()]
+
+__all__ = [
+    "Alarms",
+    "AlarmTime",
+    "IncompleteAlarmInformation",
+    "ComponentEndMissing",
+    "ComponentStartMissing",
+    "LocalTimezoneMissing"
+]
diff --git a/src/icalendar/cal.py b/src/icalendar/cal.py
index c01925ce..8522d24f 100644
--- a/src/icalendar/cal.py
+++ b/src/icalendar/cal.py
@@ -7,15 +7,20 @@
 
 import os
 from datetime import date, datetime, timedelta
-from typing import List, Optional, Tuple
+from typing import TYPE_CHECKING, List, NamedTuple, Optional, Tuple, Union
 
 import dateutil.rrule
 import dateutil.tz
+
 from icalendar.caselessdict import CaselessDict
 from icalendar.parser import Contentline, Contentlines, Parameters, q_join, q_split
 from icalendar.parser_tools import DEFAULT_ENCODING
-from icalendar.prop import TypesFactory, vDDDLists, vDDDTypes, vText, vDuration
+from icalendar.prop import TypesFactory, vDDDLists, vDDDTypes, vDuration, vText
 from icalendar.timezone import tzp
+from icalendar.tools import is_date
+
+if TYPE_CHECKING:
+    from icalendar.alarms import Alarms
 
 
 def get_example(component_directory: str, example_name: str) -> bytes:
@@ -76,9 +81,45 @@ class IncompleteComponent(ValueError):
     The attributes are not required, otherwise this would be
     an InvalidCalendar. But in order to perform calculations,
     this attribute is required.
+
+    This error is not raised in the UPPERCASE properties like .DTSTART,
+    only in the lowercase computations like .start.
+    """
+
+def create_utc_property(name:str, docs:str) -> property:
+    """Create a property to access a value of datetime in UTC timezone.
+
+    name - name of the property
+    docs - documentation string
     """
+    docs = f"""The {name} property. datetime in UTC
 
+    All values will be converted to a datetime in UTC.
+    """ + docs
 
+    def p_get(self: Component) -> Optional[datetime]:
+        """Get the value."""
+        if name not in self:
+            return None
+        dt = self.get(name)
+        if isinstance(dt, vText):
+            # we might be in an attribute that is not typed
+            value = vDDDTypes.from_ical(dt)
+        else:
+            value = getattr(dt, "dt", None)
+        if value is None or not isinstance(value, date):
+            raise InvalidCalendar(f"{name} must be a datetime in UTC, not {value}")
+        return tzp.localize_utc(value)
+
+    def p_set(self: Component, value: datetime):
+        """Set the value"""
+        if not isinstance(value, date):
+            raise TypeError(f"{name} takes a datetime in UTC, not {value}")
+        self.pop(name)
+        self.add(name, tzp.localize_utc(value))
+
+
+    return property(p_get, p_set, doc=docs)
 
 class Component(CaselessDict):
     """Component is the base object for calendar, Event and the other
@@ -494,11 +535,51 @@ def __eq__(self, other):
 
         return True
 
+    DTSTAMP = create_utc_property("DTSTAMP", """RFC 5545:
+
+        Conformance:  This property MUST be included in the "VEVENT",
+        "VTODO", "VJOURNAL", or "VFREEBUSY" calendar components.
+
+        Description: In the case of an iCalendar object that specifies a
+        "METHOD" property, this property specifies the date and time that
+        the instance of the iCalendar object was created.  In the case of
+        an iCalendar object that doesn't specify a "METHOD" property, this
+        property specifies the date and time that the information
+        associated with the calendar component was last revised in the
+        calendar store.
+
+        The value MUST be specified in the UTC time format.
+
+        In the case of an iCalendar object that doesn't specify a "METHOD"
+        property, this property is equivalent to the "LAST-MODIFIED"
+        property.
+    """)
+    LAST_MODIFIED = create_utc_property("LAST-MODIFIED", """RFC 5545:
+
+        Purpose:  This property specifies the date and time that the
+        information associated with the calendar component was last
+        revised in the calendar store.
+
+        Note: This is analogous to the modification date and time for a
+        file in the file system.
+
+        Conformance:  This property can be specified in the "VEVENT",
+        "VTODO", "VJOURNAL", or "VTIMEZONE" calendar components.
+    """)
+
+    def is_thunderbird(self) -> bool:
+        """Whether this component has attributes that indicate that Mozilla Thunderbird created it."""
+        return any(attr.startswith("X-MOZ-") for attr in self.keys())
+
+
+
 #######################################
 # components defined in RFC 5545
 
 def create_single_property(prop:str, value_attr:str, value_type:tuple[type], type_def:type, doc:str):
-    """Create a single property getter and setter."""
+    """Create a single property getter and setter.
+    
+    This is a getter and setter for a property that only occurs once or not (None)."""
 
     def p_get(self : Component):
         default = object()
@@ -540,13 +621,14 @@ def p_del(self:Component):
     return property(p_get, p_set, p_del, p_doc)
 
 
-def is_date(dt: date) -> bool:
-    """Whether this is a date and not a datetime."""
-    return isinstance(dt, date) and not isinstance(dt, datetime)
-
-def is_datetime(dt: date) -> bool:
-    """Whether this is a date and not a datetime."""
-    return isinstance(dt, datetime)
+_X_MOZ_SNOOZE_TIME = create_utc_property(
+    "X-MOZ-SNOOZE-TIME",
+    "Thunderbird: Alarms before this time are snoozed."
+)
+_X_MOZ_LASTACK = create_utc_property(
+    "X-MOZ-LASTACK",
+    "Thunderbird: Alarms before this time are acknowledged."
+)
 
 def _get_duration(self: Component) -> Optional[timedelta]:
     """Getter for property DURATION."""
@@ -619,6 +701,26 @@ class Event(Component):
         'RSTATUS', 'RELATED', 'RESOURCES', 'RDATE', 'RRULE'
     )
     ignore_exceptions = True
+    
+    @property
+    def alarms(self) -> Alarms:
+        """Compute the alarm times for this component.
+
+        >>> from icalendar import Event
+        >>> event = Event.example("rfc_9074_example_1")
+        >>> len(event.alarms.times)
+        1
+        >>> alarm_time = event.alarms.times[0]
+        >>> alarm_time.trigger  # The time when the alarm pops up
+        datetime.datetime(2021, 3, 2, 10, 15, tzinfo=ZoneInfo(key='America/New_York'))
+        >>> alarm_time.is_active()  # This alarm has not been acknowledged
+        True
+
+        Note that this only uses DTSTART and DTEND, but ignores
+        RDATE, EXDATE, and RRULE properties.
+        """
+        from icalendar.alarms import Alarms
+        return Alarms(self)
 
     @classmethod
     def example(cls, name:str) -> Event:
@@ -710,6 +812,9 @@ def end(self, end: date | datetime | None):
         """Set the end."""
         self.DTEND = end
 
+    X_MOZ_SNOOZE_TIME = _X_MOZ_SNOOZE_TIME
+    X_MOZ_LASTACK = _X_MOZ_LASTACK
+
 
 class Todo(Component):
     """
@@ -818,6 +923,26 @@ def duration(self) -> timedelta:
         """
         return self.end - self.start
 
+    X_MOZ_SNOOZE_TIME = _X_MOZ_SNOOZE_TIME
+    X_MOZ_LASTACK = _X_MOZ_LASTACK
+
+    @property
+    def alarms(self) -> Alarms:
+        """Compute the alarm times for this component.
+
+        >>> from datetime import datetime
+        >>> from icalendar import Todo
+        >>> todo = Todo()  # empty without alarms
+        >>> todo.start = datetime(2024, 10, 26, 10, 21)
+        >>> len(todo.alarms.times)
+        0
+
+        Note that this only uses DTSTART and DUE, but ignores
+        RDATE, EXDATE, and RRULE properties.
+        """
+        from icalendar.alarms import Alarms
+        return Alarms(self)
+
 
 class Journal(Component):
     """A descriptive text at a certain time or associated with a component.
@@ -1103,6 +1228,168 @@ class Alarm(Component):
     multiple = ('ATTENDEE', 'ATTACH', 'RELATED-TO')
 
 
+    @property
+    def REPEAT(self) -> int:
+        """The REPEAT property of an alarm component.
+
+        The alarm can be defined such that it triggers repeatedly.  A
+        definition of an alarm with a repeating trigger MUST include both
+        the "DURATION" and "REPEAT" properties.  The "DURATION" property
+        specifies the delay period, after which the alarm will repeat.
+        The "REPEAT" property specifies the number of additional
+        repetitions that the alarm will be triggered.  This repetition
+        count is in addition to the initial triggering of the alarm.
+        """
+        try:
+            return int(self.get("REPEAT", 0))
+        except ValueError as e:
+            raise InvalidCalendar("REPEAT must be an int") from e
+
+    @REPEAT.setter
+    def REPEAT(self, value: int) -> None:
+        """The REPEAT property of an alarm component."""
+        self["REPEAT"] = int(value)
+
+    DURATION = property(_get_duration, _set_duration, _del_duration,
+    """The DURATION property of an alarm component.
+
+    The alarm can be defined such that it triggers repeatedly.  A
+    definition of an alarm with a repeating trigger MUST include both
+    the "DURATION" and "REPEAT" properties.  The "DURATION" property
+    specifies the delay period, after which the alarm will repeat.
+    """)
+
+    ACKNOWLEDGED = create_utc_property("ACKNOWLEDGED",
+    """This is defined in RFC 9074:
+
+    Purpose: This property specifies the UTC date and time at which the
+    corresponding alarm was last sent or acknowledged.
+
+    This property is used to specify when an alarm was last sent or acknowledged.
+    This allows clients to determine when a pending alarm has been acknowledged
+    by a calendar user so that any alerts can be dismissed across multiple devices.
+    It also allows clients to track repeating alarms or alarms on recurring events or
+    to-dos to ensure that the right number of missed alarms can be tracked.
+
+    Clients SHOULD set this property to the current date-time value in UTC
+    when a calendar user acknowledges a pending alarm. Certain kinds of alarms,
+    such as email-based alerts, might not provide feedback as to when the calendar user
+    sees them. For those kinds of alarms, the client SHOULD set this property
+    when the alarm is triggered and the action is successfully carried out.
+
+    When an alarm is triggered on a client, clients can check to see if an "ACKNOWLEDGED"
+    property is present. If it is, and the value of that property is greater than or
+    equal to the computed trigger time for the alarm, then the client SHOULD NOT trigger
+    the alarm. Similarly, if an alarm has been triggered and
+    an "alert" has been presented to a calendar user, clients can monitor
+    the iCalendar data to determine whether an "ACKNOWLEDGED" property is added or
+    changed in the alarm component. If the value of any "ACKNOWLEDGED" property
+    in the alarm changes and is greater than or equal to the trigger time of the alarm,
+    then clients SHOULD dismiss or cancel any "alert" presented to the calendar user.
+    """)
+
+    TRIGGER = create_single_property(
+        "TRIGGER", "dt", (datetime, timedelta), Optional[Union[timedelta, datetime]],
+    """Purpose:  This property specifies when an alarm will trigger.
+
+    Value Type:  The default value type is DURATION.  The value type can
+    be set to a DATE-TIME value type, in which case the value MUST
+    specify a UTC-formatted DATE-TIME value.
+
+    Either a positive or negative duration may be specified for the
+    "TRIGGER" property.  An alarm with a positive duration is
+    triggered after the associated start or end of the event or to-do.
+    An alarm with a negative duration is triggered before the
+    associated start or end of the event or to-do."""
+    )
+
+    @property
+    def TRIGGER_RELATED(self) -> str:
+        """The RELATED parameter of the TRIGGER property.
+
+        Values are either "START" (default) or "END".
+
+        A value of START will set the alarm to trigger off the
+        start of the associated event or to-do.  A value of END will set
+        the alarm to trigger off the end of the associated event or to-do.
+
+        In this example, we create an alarm that triggers two hours after the
+        end of its parent component:
+
+        >>> from icalendar import Alarm
+        >>> from datetime import timedelta
+        >>> alarm = Alarm()
+        >>> alarm.TRIGGER = timedelta(hours=2)
+        >>> alarm.TRIGGER_RELATED = "END"
+        """
+        trigger = self.get("TRIGGER")
+        if trigger is None:
+            return "START"
+        return trigger.params.get("RELATED", "START")
+
+    @TRIGGER_RELATED.setter
+    def TRIGGER_RELATED(self, value: str):
+        """Set "START" or "END"."""
+        trigger = self.get("TRIGGER")
+        if trigger is None:
+            raise ValueError("You must set a TRIGGER before setting the RELATED parameter.")
+        trigger.params["RELATED"] = value
+    
+    class Triggers(NamedTuple):
+        """The computed times of alarm triggers.
+
+        start - triggers relative to the start of the Event or Todo (timedelta)
+        
+        end - triggers relative to the end of the Event or Todo (timedelta)
+        
+        absolute - triggers at a datetime in UTC
+        """
+        start: tuple[timedelta]
+        end: tuple[timedelta]
+        absolute: tuple[datetime]
+    
+    @property
+    def triggers(self):
+        """The computed triggers of an Alarm.
+
+        This takes the TRIGGER, DURATION and REPEAT properties into account.
+
+        Here, we create an alarm that triggers 3 times before the start of the
+        parent component:
+
+        >>> from icalendar import Alarm
+        >>> from datetime import timedelta
+        >>> alarm = Alarm()
+        >>> alarm.TRIGGER = timedelta(hours=-4)  # trigger 4 hours before START
+        >>> alarm.DURATION = timedelta(hours=1)  # after 1 hour trigger again
+        >>> alarm.REPEAT = 2  # trigger 2 more times
+        >>> alarm.triggers.start == (timedelta(hours=-4),  timedelta(hours=-3),  timedelta(hours=-2))
+        True
+        >>> alarm.triggers.end
+        ()
+        >>> alarm.triggers.absolute
+        ()
+        """
+        start = []
+        end = []
+        absolute = []
+        trigger = self.TRIGGER
+        if trigger is not None:
+            if isinstance(trigger, date):
+                absolute.append(trigger)
+                add = absolute
+            elif self.TRIGGER_RELATED == "START":
+                start.append(trigger)
+                add = start
+            else:
+                end.append(trigger)
+                add = end
+            duration = self.DURATION
+            if duration is not None:
+                for _ in range(self.REPEAT):
+                    add.append(add[-1] + duration)
+        return self.Triggers(start=tuple(start), end=tuple(end), absolute=tuple(absolute))
+
 class Calendar(Component):
     """
     The "VCALENDAR" object is a collection of calendar information.
diff --git a/src/icalendar/prop.py b/src/icalendar/prop.py
index c2969ecc..2e5ac643 100644
--- a/src/icalendar/prop.py
+++ b/src/icalendar/prop.py
@@ -35,28 +35,25 @@
 These types are mainly used for parsing and file generation. But you can set
 them directly.
 """
-from datetime import date
-from datetime import datetime
-from datetime import time
-from datetime import timedelta
-from datetime import tzinfo
-from icalendar.caselessdict import CaselessDict
-from icalendar.parser import Parameters
-from icalendar.parser import escape_char
-from icalendar.parser import unescape_char
-from icalendar.parser_tools import (
-    DEFAULT_ENCODING, SEQUENCE_TYPES, to_unicode, from_unicode, ICAL_TYPE
-)
-
 import base64
 import binascii
-from .timezone import tzp
 import re
 import time as _time
-
-from typing import Optional, Union
+from datetime import date, datetime, time, timedelta, tzinfo
 from enum import Enum, auto
+from typing import Optional, Union
+
+from icalendar.caselessdict import CaselessDict
+from icalendar.parser import Parameters, escape_char, unescape_char
+from icalendar.parser_tools import (
+    DEFAULT_ENCODING,
+    ICAL_TYPE,
+    SEQUENCE_TYPES,
+    from_unicode,
+    to_unicode,
+)
 
+from . import timezone as _timezone
 
 DURATION_REGEX = re.compile(r'([-+]?)P(?:(\d+)W)?(?:(\d+)D)?'
                             r'(?:T(?:(\d+)H)?(?:(\d+)M)?(?:(\d+)S)?)?$')
@@ -408,9 +405,28 @@ def to_ical(self):
 
     @staticmethod
     def from_ical(ical, timezone=None):
+        """Create a datetime from the RFC string.
+
+        Format: YYYYMMDDTHHMMSS
+
+        >>> from icalendar import vDatetime
+        >>> vDatetime.from_ical("20210302T101500")
+        datetime.datetime(2021, 3, 2, 10, 15)
+
+        >>> vDatetime.from_ical("20210302T101500", "America/New_York")
+        datetime.datetime(2021, 3, 2, 10, 15, tzinfo=ZoneInfo(key='America/New_York'))
+
+        >>> from zoneinfo import ZoneInfo
+        >>> timezone = ZoneInfo("Europe/Berlin")
+        >>> vDatetime.from_ical("20210302T101500", timezone)
+        datetime.datetime(2021, 3, 2, 10, 15, tzinfo=ZoneInfo(key='Europe/Berlin'))
+
+        """
         tzinfo = None
-        if timezone:
-            tzinfo = tzp.timezone(timezone)
+        if isinstance(timezone, str):
+            tzinfo = _timezone.tzp.timezone(timezone)
+        elif timezone is not None:
+            tzinfo = timezone
 
         try:
             timetuple = (
@@ -422,15 +438,15 @@ def from_ical(ical, timezone=None):
                 int(ical[13:15]),  # second
             )
             if tzinfo:
-                return tzp.localize(datetime(*timetuple), tzinfo)
+                return _timezone.tzp.localize(datetime(*timetuple), tzinfo)
             elif not ical[15:]:
                 return datetime(*timetuple)
             elif ical[15:16] == 'Z':
-                return tzp.localize_utc(datetime(*timetuple))
+                return _timezone.tzp.localize_utc(datetime(*timetuple))
             else:
                 raise ValueError(ical)
-        except Exception:
-            raise ValueError(f'Wrong datetime format: {ical}')
+        except Exception as e:
+            raise ValueError(f'Wrong datetime format: {ical}') from e
 
 
 class vDuration(TimeBase):
diff --git a/src/icalendar/tests/alarms/rfc_5545_absolute_alarm_example.ics b/src/icalendar/tests/alarms/rfc_5545_absolute_alarm_example.ics
new file mode 100644
index 00000000..9f7f71f3
--- /dev/null
+++ b/src/icalendar/tests/alarms/rfc_5545_absolute_alarm_example.ics
@@ -0,0 +1,7 @@
+BEGIN:VALARM
+TRIGGER;VALUE=DATE-TIME:19970317T133000Z
+REPEAT:4
+DURATION:PT15M
+ACTION:AUDIO
+ATTACH;FMTTYPE=audio/basic:ftp://example.com/pub/sounds/bell-01.aud
+END:VALARM
diff --git a/src/icalendar/tests/alarms/rfc_5545_end.ics b/src/icalendar/tests/alarms/rfc_5545_end.ics
new file mode 100644
index 00000000..a9f52ddd
--- /dev/null
+++ b/src/icalendar/tests/alarms/rfc_5545_end.ics
@@ -0,0 +1,8 @@
+BEGIN:VALARM
+TRIGGER;RELATED=END:-P2D
+ACTION:EMAIL
+ATTENDEE:mailto:john_doe@example.com
+SUMMARY:*** REMINDER: SEND AGENDA FOR WEEKLY STAFF MEETING ***
+DESCRIPTION:A draft agenda needs to be sent out to the attendees to the weekly managers meeting (MGR-LIST). Attached is a pointer the document template for the agenda file.
+ATTACH;FMTTYPE=application/msword:http://example.com/templates/agenda.doc
+END:VALARM
diff --git a/src/icalendar/tests/alarms/start_date.ics b/src/icalendar/tests/alarms/start_date.ics
new file mode 100644
index 00000000..cc87c948
--- /dev/null
+++ b/src/icalendar/tests/alarms/start_date.ics
@@ -0,0 +1,8 @@
+BEGIN:VALARM
+TRIGGER;RELATED=START:-P2D
+ACTION:EMAIL
+ATTENDEE:mailto:john_doe@example.com
+SUMMARY:*** REMINDER: SEND AGENDA FOR WEEKLY STAFF MEETING ***
+DESCRIPTION:A draft agenda needs to be sent out to the attendees to the weekly managers meeting (MGR-LIST). Attached is a pointer the document template for the agenda file.
+ATTACH;FMTTYPE=application/msword:http://example.com/templates/agenda.doc
+END:VALARM
diff --git a/src/icalendar/tests/calendars/alarm_etar_future.ics b/src/icalendar/tests/calendars/alarm_etar_future.ics
new file mode 100644
index 00000000..d2735f5d
--- /dev/null
+++ b/src/icalendar/tests/calendars/alarm_etar_future.ics
@@ -0,0 +1,235 @@
+BEGIN:VCALENDAR
+PRODID:-//Offline Calendar//iCal Import/Export 2.8.1//EN
+VERSION:2.0
+METHOD:PUBLISH
+CALSCALE:GREGORIAN
+BEGIN:VTIMEZONE
+TZID:Europe/London
+TZURL:http://tzurl.org/zoneinfo/Europe/London
+X-LIC-LOCATION:Europe/London
+BEGIN:DAYLIGHT
+TZOFFSETFROM:+0000
+TZOFFSETTO:+0100
+TZNAME:BST
+DTSTART:19810329T010000
+RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=-1SU
+END:DAYLIGHT
+BEGIN:STANDARD
+TZOFFSETFROM:+0100
+TZOFFSETTO:+0000
+TZNAME:GMT
+DTSTART:19961027T020000
+RRULE:FREQ=YEARLY;BYMONTH=10;BYDAY=-1SU
+END:STANDARD
+BEGIN:STANDARD
+TZOFFSETFROM:-000115
+TZOFFSETTO:+0000
+TZNAME:GMT
+DTSTART:18471201T000115
+RDATE:18471201T000115
+END:STANDARD
+BEGIN:DAYLIGHT
+TZOFFSETFROM:+0000
+TZOFFSETTO:+0100
+TZNAME:BST
+DTSTART:19160521T020000
+RDATE:19160521T020000
+RDATE:19170408T020000
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+DTSTART:19960101T000000
+RDATE:19960101T000000
+END:STANDARD
+END:VTIMEZONE
+BEGIN:VEVENT
+DTSTAMP:20241005T112701Z
+UID:17281276213728ad54d03afa44d1ca60b8c52afaece9e@sufficientlysecure.org
+SUMMARY:event with alarms android
+STATUS:CONFIRMED
+DTSTART;TZID=Europe/London:20241005T130000
+DTEND:20241005T130000Z
+LAST-MODIFIED:20241005T112701Z
+BEGIN:VALARM
+TRIGGER:-PT30M
+ACTION:DISPLAY
+DESCRIPTION:event with alarms android
+END:VALARM
+BEGIN:VALARM
+TRIGGER:-PT25M
+ACTION:DISPLAY
+DESCRIPTION:event with alarms android
+END:VALARM
+BEGIN:VALARM
+TRIGGER:-PT5M
+ACTION:DISPLAY
+DESCRIPTION:event with alarms android
+END:VALARM
+END:VEVENT
+END:VCALENDAR
diff --git a/src/icalendar/tests/calendars/alarm_etar_notification.ics b/src/icalendar/tests/calendars/alarm_etar_notification.ics
new file mode 100644
index 00000000..bbee664b
--- /dev/null
+++ b/src/icalendar/tests/calendars/alarm_etar_notification.ics
@@ -0,0 +1,235 @@
+BEGIN:VCALENDAR
+PRODID:-//Offline Calendar//iCal Import/Export 2.8.1//EN
+VERSION:2.0
+METHOD:PUBLISH
+CALSCALE:GREGORIAN
+BEGIN:VTIMEZONE
+TZID:Europe/London
+TZURL:http://tzurl.org/zoneinfo/Europe/London
+X-LIC-LOCATION:Europe/London
+BEGIN:DAYLIGHT
+TZOFFSETFROM:+0000
+TZOFFSETTO:+0100
+TZNAME:BST
+DTSTART:19810329T010000
+RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=-1SU
+END:DAYLIGHT
+BEGIN:STANDARD
+TZOFFSETFROM:+0100
+TZOFFSETTO:+0000
+TZNAME:GMT
+DTSTART:19961027T020000
+RRULE:FREQ=YEARLY;BYMONTH=10;BYDAY=-1SU
+END:STANDARD
+BEGIN:STANDARD
+TZOFFSETFROM:-000115
+TZOFFSETTO:+0000
+TZNAME:GMT
+DTSTART:18471201T000115
+RDATE:18471201T000115
+END:STANDARD
+BEGIN:DAYLIGHT
+TZOFFSETFROM:+0000
+TZOFFSETTO:+0100
+TZNAME:BST
+DTSTART:19160521T020000
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index 00000000..c61e048f
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+++ b/src/icalendar/tests/calendars/alarm_etar_notification_clicked.ics
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+SUMMARY:event with alarm acknowledged
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diff --git a/src/icalendar/tests/calendars/alarm_google_acknowledged.ics b/src/icalendar/tests/calendars/alarm_google_acknowledged.ics
new file mode 100644
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--- /dev/null
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+BEGIN:VCALENDAR
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+CREATED:20241004T175920Z
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diff --git a/src/icalendar/tests/calendars/alarm_google_future.ics b/src/icalendar/tests/calendars/alarm_google_future.ics
new file mode 100644
index 00000000..f7e4e7ef
--- /dev/null
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+TZNAME:Europe/London(DST)
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+RRULE:FREQ=YEARLY;BYMONTH=10;BYDAY=-1SU
+END:STANDARD
+END:VTIMEZONE
+BEGIN:VEVENT
+CREATED:20241023T131035Z
+LAST-MODIFIED:20241023T135202Z
+DTSTAMP:20241023T135202Z
+UID:b9a23b47-f109-4e7a-908c-75e925b27def
+SUMMARY:event with alarms
+X-MOZ-LASTACK:20241023T135202Z
+DTSTART;TZID=Europe/London:20241023T150000
+DTEND;TZID=Europe/London:20241023T160000
+TRANSP:OPAQUE
+X-MOZ-GENERATION:4
+X-MOZ-SNOOZE-TIME:20241023T135702Z
+BEGIN:VALARM
+ACTION:DISPLAY
+TRIGGER:-PT15M
+DESCRIPTION:Mozilla Standardbeschreibung
+END:VALARM
+BEGIN:VALARM
+ACTION:DISPLAY
+TRIGGER:-PT45M
+DESCRIPTION:Mozilla Standardbeschreibung
+END:VALARM
+END:VEVENT
+END:VCALENDAR
diff --git a/src/icalendar/tests/conftest.py b/src/icalendar/tests/conftest.py
index 8db1941e..3062b6d2 100644
--- a/src/icalendar/tests/conftest.py
+++ b/src/icalendar/tests/conftest.py
@@ -93,6 +93,7 @@ def multiple(self):
 CALENDARS_FOLDER = HERE / "calendars"
 TIMEZONES_FOLDER = HERE / "timezones"
 EVENTS_FOLDER = HERE / "events"
+ALARMS_FOLDER = HERE / "alarms"
 
 
 @pytest.fixture(scope="module")
@@ -110,6 +111,11 @@ def events(tzp):
     return DataSource(EVENTS_FOLDER, icalendar.Event.from_ical)
 
 
+@pytest.fixture(scope="module")
+def alarms(tzp):
+    return DataSource(ALARMS_FOLDER, icalendar.Alarm.from_ical)
+
+
 @pytest.fixture(params=PYTZ_UTC + [zoneinfo.ZoneInfo("UTC"), tz.UTC, tz.gettz("UTC")])
 def utc(request, tzp):
     return request.param
diff --git a/src/icalendar/tests/prop/test_alarm.py b/src/icalendar/tests/prop/test_alarm.py
new file mode 100644
index 00000000..7decf33a
--- /dev/null
+++ b/src/icalendar/tests/prop/test_alarm.py
@@ -0,0 +1,57 @@
+"""Test the properties of the alarm."""
+
+
+import pytest
+
+from icalendar.cal import Alarm, InvalidCalendar
+
+
+def test_repeat_absent():
+    """Test the absence of REPEAT."""
+    assert Alarm().REPEAT == 0
+
+
+def test_repeat_number():
+    """Test the absence of REPEAT."""
+    assert Alarm({"REPEAT": 10}).REPEAT == 10
+
+
+def test_set_REPEAT():
+    """Check setting the value."""
+    a = Alarm()
+    a.REPEAT = 10
+    assert a.REPEAT == 10
+
+
+def test_set_REPEAT_twice():
+    """Check setting the value."""
+    a = Alarm()
+    a.REPEAT = 10
+    a.REPEAT = 20
+    assert a.REPEAT == 20
+
+
+def test_add_REPEAT():
+    """Check setting the value."""
+    a = Alarm()
+    a.add("REPEAT", 10)
+    assert a.REPEAT == 10
+
+
+def test_invalid_repeat_value():
+    """Check setting the value."""
+    a = Alarm()
+    with pytest.raises(ValueError):
+        a.REPEAT = "asd"
+    a["REPEAT"] = "asd"
+    with pytest.raises(InvalidCalendar):
+        a.REPEAT  # noqa: B018
+
+
+def test_alarm_to_string():
+    a = Alarm()
+    a.REPEAT = 11
+    assert a.to_ical() == b"BEGIN:VALARM\r\nREPEAT:11\r\nEND:VALARM\r\n"
+
+
+
diff --git a/src/icalendar/tests/prop/test_component.py b/src/icalendar/tests/prop/test_component.py
new file mode 100644
index 00000000..adc5e21f
--- /dev/null
+++ b/src/icalendar/tests/prop/test_component.py
@@ -0,0 +1,97 @@
+"""Test common properties of components."""
+
+from datetime import date, datetime, timedelta
+
+import pytest
+
+from icalendar import Event, FreeBusy, Journal, Todo, vDDDTypes
+from icalendar.cal import Component, InvalidCalendar
+
+
+@pytest.fixture(params=[Event, Todo, Journal, FreeBusy])
+def dtstamp_comp(request):
+    """a component to test"""
+    return request.param()
+
+
+def test_no_dtstamp(dtstamp_comp):
+    """We have None as a value."""
+    assert dtstamp_comp.DTSTAMP is None
+
+
+def set_dtstamp_attribute(component:Component, value:date):
+    """Use the setter."""
+    component.DTSTAMP = value
+
+def set_dtstamp_item(component: Component, value:date):
+    """Use setitem."""
+    component["DTSTAMP"] = vDDDTypes(value)
+
+def set_dtstamp_add(component: Component, value:date):
+    """Use add."""
+    component.add("DTSTAMP", value)
+
+
+
+@pytest.mark.parametrize(
+    ("value", "timezone", "expected"),
+    [
+        (datetime(2024, 10, 11, 23, 1), None, datetime(2024, 10, 11, 23, 1)),
+        (datetime(2024, 10, 11, 23, 1), "Europe/Berlin", datetime(2024, 10, 11, 21, 1)),
+        (datetime(2024, 10, 11, 22, 1), "UTC", datetime(2024, 10, 11, 22, 1)),
+        (date(2024, 10, 10), None, datetime(2024, 10, 10)),
+    ]
+)
+@pytest.mark.parametrize(
+    "set_dtstamp", [set_dtstamp_add, set_dtstamp_attribute, set_dtstamp_item]
+)
+def test_set_value_and_get_it(dtstamp_comp, value, timezone, expected, tzp, set_dtstamp):
+    """Set and get the DTSTAMP value."""
+    dtstamp = value if timezone is None else tzp.localize(value, timezone)
+    set_dtstamp(dtstamp_comp, dtstamp)
+    in_utc = tzp.localize_utc(expected)
+    get_value = dtstamp_comp.get("DTSTAMP").dt
+    assert in_utc == get_value or set_dtstamp != set_dtstamp_attribute
+    assert in_utc == dtstamp_comp.DTSTAMP
+
+
+@pytest.mark.parametrize(
+    "invalid_value",
+    [
+        None,
+        timedelta()
+    ]
+)
+def test_set_invalid_value(invalid_value, dtstamp_comp):
+    """Check handling of invalid values."""
+    with pytest.raises(TypeError) as e:
+        dtstamp_comp.DTSTAMP = invalid_value
+    assert e.value.args[0] == f"DTSTAMP takes a datetime in UTC, not {invalid_value}"
+
+
+@pytest.mark.parametrize(
+    "invalid_value",
+    [
+        None,
+        vDDDTypes(timedelta())
+    ]
+)
+def test_get_invalid_value(invalid_value, dtstamp_comp):
+    """Check handling of invalid values."""
+    dtstamp_comp["DTSTAMP"] = invalid_value
+    with pytest.raises(InvalidCalendar) as e:
+        dtstamp_comp.DTSTAMP  # noqa: B018
+    assert e.value.args[0] == f"DTSTAMP must be a datetime in UTC, not {getattr(invalid_value, 'dt', invalid_value)}"
+
+
+def test_set_twice(dtstamp_comp, tzp):
+    """Set the value twice."""
+    dtstamp_comp.DTSTAMP = date(2014, 1, 1)
+    dtstamp_comp.DTSTAMP = date(2014, 1, 2)
+    assert tzp.localize_utc(datetime(2014, 1, 2)) == dtstamp_comp.DTSTAMP
+
+
+def test_last_modified(dtstamp_comp, tzp):
+    """Check we can set LAST_MODIFIED in the same way as DTSTAMP"""
+    dtstamp_comp.LAST_MODIFIED = date(2014, 1, 2)
+    assert tzp.localize_utc(datetime(2014, 1, 2)) == dtstamp_comp.LAST_MODIFIED
diff --git a/src/icalendar/tests/test_issue_662_component_properties.py b/src/icalendar/tests/test_issue_662_component_properties.py
index 095e94a6..b524c95a 100644
--- a/src/icalendar/tests/test_issue_662_component_properties.py
+++ b/src/icalendar/tests/test_issue_662_component_properties.py
@@ -4,6 +4,8 @@
 
 import pytest
 
+from icalendar.cal import Alarm
+
 try:
     from zoneinfo import ZoneInfo
 except ImportError:
@@ -16,6 +18,7 @@
     Journal,
     Todo,
     vDDDTypes,
+    vDatetime,
 )
 from icalendar.prop import vDuration
 
@@ -493,3 +496,108 @@ def setting_twice_does_not_duplicate_the_entry():
     assert j.start == date(2024, 1, 3)
     assert j.end == date(2024, 1, 3)
 
+
+@pytest.mark.parametrize(
+    ("file", "trigger", "related"),
+    [
+        ("rfc_5545_absolute_alarm_example", vDatetime.from_ical("19970317T133000Z"), "START"),
+        ("rfc_5545_end", timedelta(days=-2), "END"),
+        ("start_date", timedelta(days=-2), "START"),
+    ]
+)
+def test_get_alarm_trigger_property(alarms, file, trigger, related):
+    """Get the trigger property."""
+    alarm = alarms[file]
+    assert alarm.TRIGGER == trigger
+    assert alarm.TRIGGER_RELATED == related
+
+
+def test_set_alarm_trigger():
+    """Set the alarm trigger."""
+    a = Alarm()
+    a.TRIGGER = timedelta(hours=1)
+    assert a.TRIGGER == timedelta(hours=1)
+    assert a.TRIGGER_RELATED == "START"
+
+
+def test_set_alarm_trigger_related():
+    """Set the alarm trigger."""
+    a = Alarm()
+    a.TRIGGER = timedelta(hours=1)
+    a.TRIGGER_RELATED = "END"
+    assert a.TRIGGER == timedelta(hours=1)
+    assert a.TRIGGER_RELATED == "END"
+
+
+def test_get_related_without_trigger():
+    """The default is start"""
+    assert Alarm().TRIGGER_RELATED == "START"
+
+def test_cannot_set_related_without_trigger():
+    """TRIGGER must be set to set the parameter."""
+    with pytest.raises(ValueError) as e:
+        a = Alarm()
+        a.TRIGGER_RELATED = "END"
+    assert e.value.args[0] == "You must set a TRIGGER before setting the RELATED parameter."
+
+
+@pytest.mark.parametrize(
+    ("file", "triggers"),
+    [
+        ("rfc_5545_absolute_alarm_example", ((), (), (vDatetime.from_ical("19970317T133000Z"), vDatetime.from_ical("19970317T134500Z"),vDatetime.from_ical("19970317T140000Z"),vDatetime.from_ical("19970317T141500Z"),vDatetime.from_ical("19970317T143000Z"),))),
+        ("rfc_5545_end", ((), (timedelta(days=-2),), ())),
+        ("start_date", ((timedelta(days=-2),), (), ())),
+    ]
+)
+def test_get_alarm_triggers(alarms, file, triggers):
+    """Get the trigger property."""
+    alarm = alarms[file]
+    print(tuple(alarm.triggers))
+    print(triggers)
+    assert alarm.triggers == triggers
+
+
+def test_triggers_emtpy_alarm():
+    """An alarm with no trigger has no triggers."""
+    assert Alarm().triggers == ((), (), ())
+
+h1 = timedelta(hours=1)
+
+def test_triggers_emtpy_with_no_repeat():
+    """Check incomplete values."""
+    a = Alarm()
+    a.TRIGGER = h1
+    a.DURATION = h1
+    assert a.triggers == ((h1,), (), ())
+
+def test_triggers_emtpy_with_no_duration():
+    """Check incomplete values."""
+    a = Alarm()
+    a.TRIGGER = h1
+    a.REPEAT = 10
+    assert a.triggers == ((h1,), (), ())
+
+
+@pytest.mark.parametrize(
+    ("file", "triggers"),
+    [
+        ("rfc_5545_absolute_alarm_example", ((), (), (vDatetime.from_ical("19970317T133000Z"),))),
+        ("rfc_5545_end", ((), (timedelta(days=-2),), ())),
+        ("start_date", ((timedelta(days=-2),), (), ())),
+    ]
+)
+@pytest.mark.parametrize("duration", [timedelta(days=-1), h1])
+@pytest.mark.parametrize("repeat", [1, 3])
+def test_get_alarm_triggers_repeated(alarms, file, triggers, duration, repeat):
+    """Get the trigger property."""
+    alarm = alarms[file].copy()
+    alarm.REPEAT = repeat
+    alarm.DURATION = duration
+    for expected, triggers in zip(triggers, alarm.triggers):
+        if not expected:
+            assert triggers == ()
+            continue
+        assert len(triggers) == 1 + repeat
+        assert triggers[0] == expected[0]
+        for x, y in zip(triggers[:-1], triggers[1:]):
+            assert y - x == duration
diff --git a/src/icalendar/tests/test_issue_716_alarm_extension.py b/src/icalendar/tests/test_issue_716_alarm_extension.py
deleted file mode 100644
index b6beead9..00000000
--- a/src/icalendar/tests/test_issue_716_alarm_extension.py
+++ /dev/null
@@ -1,13 +0,0 @@
-"""Test the alarm classification.
-
-Events can have alarms.
-Alarms can be in this state:
-
-- active - the user wants the alarm to pop up
-- acknowledged - the user no longer wants the alarm
-- snoozed - the user moved that alarm to another time
-
-The alarms can only work on the properties of the event like
-DTSTART, DTEND and DURATION.
-
-"""
diff --git a/src/icalendar/tests/test_issue_716_alarm_time_computation.py b/src/icalendar/tests/test_issue_716_alarm_time_computation.py
new file mode 100644
index 00000000..3f31368f
--- /dev/null
+++ b/src/icalendar/tests/test_issue_716_alarm_time_computation.py
@@ -0,0 +1,347 @@
+"""Test the alarm time computation.
+
+Events can have alarms.
+Alarms can be in this state:
+
+- active - the user wants the alarm to pop up
+- acknowledged - the user no longer wants the alarm
+- snoozed - the user moved that alarm to another time
+
+The alarms can only work on the properties of the event like
+DTSTART, DTEND, and DURATION.
+
+"""
+
+
+from datetime import date, datetime, timedelta, timezone
+
+import pytest
+
+from icalendar import Event
+from icalendar.alarms import Alarms, IncompleteAlarmInformation
+from icalendar.cal import Alarm
+from icalendar.prop import vDatetime
+from icalendar.tools import normalize_pytz
+
+UTC = timezone.utc
+EXAMPLE_TRIGGER = datetime(1997, 3, 17, 13, 30, tzinfo=UTC)
+
+
+def test_absolute_alarm_time_rfc_example(alarms):
+    """Check that the absolute alarm is recognized.
+
+    The following example is for a "VALARM" calendar component
+    that specifies an audio alarm that will sound at a precise time
+    and repeat 4 more times at 15-minute intervals:
+    """
+    a = Alarms(alarms.rfc_5545_absolute_alarm_example)
+    times = a.times
+    assert len(times) == 5
+    for i, t in enumerate(times):
+        assert t.trigger == EXAMPLE_TRIGGER + timedelta(minutes=15 * i)
+
+
+alarm_1 = Alarm()
+alarm_1.add("TRIGGER", EXAMPLE_TRIGGER)
+alarm_2 = Alarm()
+alarm_2["TRIGGER"] = vDatetime(EXAMPLE_TRIGGER)
+
+@pytest.mark.parametrize(
+    "alarm",
+    [
+        alarm_1, alarm_2
+    ]
+)
+def test_absolute_alarm_time_with_vDatetime(alarm):
+    """Check that the absolute alarm is recognized.
+
+    The following example is for a "VALARM" calendar component
+    that specifies an audio alarm that will sound at a precise time
+    and repeat 4 more times at 15-minute intervals:
+    """
+    a = Alarms(alarm)
+    times = a.times
+    assert len(times) == 1
+    assert times[0].trigger == EXAMPLE_TRIGGER
+
+
+alarm_incomplete_1 = Alarm()
+alarm_incomplete_1.TRIGGER = timedelta(hours=2)
+alarm_incomplete_1.DURATION = timedelta(hours=1)
+alarm_incomplete_2 = Alarm()
+alarm_incomplete_2.TRIGGER = timedelta(hours=2)
+alarm_incomplete_2.REPEAT = 100
+
+@pytest.mark.parametrize("alarm", [alarm_incomplete_1, alarm_incomplete_2])
+def test_alarm_has_only_one_of_repeat_or_duration(alarm):
+    """This is an edge case and we should ignore the repetition."""
+    a = Alarms(alarm)
+    a.set_start(datetime(2027, 12, 2))
+    assert len(a.times) == 1
+
+
+@pytest.fixture(params=[(0, timedelta(minutes=-30)), (1, timedelta(minutes=-25))])
+def alarm_before_start(calendars, request):
+    """An example alarm relative to the start of a component."""
+    index, td = request.param
+    alarm = calendars.alarm_etar_future.subcomponents[-1].subcomponents[index]
+    assert isinstance(alarm, Alarm)
+    assert alarm.get("TRIGGER").dt == td
+    alarm.test_td = td
+    return alarm
+
+
+def test_cannot_compute_relative_alarm_without_start(alarm_before_start):
+    """We have an alarm without a start of a component."""
+    with pytest.raises(IncompleteAlarmInformation) as e:
+        Alarms(alarm_before_start).times  # noqa: B018
+    assert e.value.args[0] == f"Use {Alarms.__name__}.{Alarms.set_start.__name__} because at least one alarm is relative to the start of a component."
+
+
+@pytest.mark.parametrize(
+    ("dtstart", "timezone", "trigger"),
+    [
+        (datetime(2024, 10, 29, 13, 10), "UTC", datetime(2024, 10, 29, 13, 10, tzinfo=UTC)),
+        (date(2024, 11, 16), None, datetime(2024, 11, 16, 0, 0)),
+        (datetime(2024, 10, 29, 13, 10), "Asia/Singapore", datetime(2024, 10, 29, 5, 10, tzinfo=UTC)),
+        (datetime(2024, 10, 29, 13, 20), None, datetime(2024, 10, 29, 13, 20)),
+    ]
+)
+def test_can_complete_relative_calculation_if_a_start_is_given(alarm_before_start, dtstart, timezone, trigger, tzp):
+    """The start is given and required."""
+    start = (dtstart if timezone is None else tzp.localize(dtstart, timezone))
+    alarms = Alarms(alarm_before_start)
+    alarms.set_start(start)
+    assert len(alarms.times) == 1
+    time = alarms.times[0]
+    expected_trigger = normalize_pytz(trigger + alarm_before_start.test_td)
+    assert time.trigger == expected_trigger
+
+
+@pytest.mark.parametrize("dtstart", [date(1998, 10, 1), date(2023, 12, 31)])
+def test_start_as_date_with_delta_as_date_stays_date(alarms, dtstart):
+    """If we have an alarm with a day delta and the event is a day event, we should stay as a date."""
+    a = Alarms(alarms.start_date)
+    a.set_start(dtstart)
+    assert len(a.times) == 1
+    assert a.times[0].trigger == dtstart - timedelta(days=2)
+
+
+def test_cannot_compute_relative_alarm_without_end(alarms):
+    """We have an alarm without an end of a component."""
+    with pytest.raises(IncompleteAlarmInformation) as e:
+        Alarms(alarms.rfc_5545_end).times  # noqa: B018
+    assert e.value.args[0] == f"Use {Alarms.__name__}.{Alarms.set_end.__name__} because at least one alarm is relative to the end of a component."
+
+
+@pytest.mark.parametrize(
+    ("dtend", "timezone", "trigger"),
+    [
+        (datetime(2024, 10, 29, 13, 10), "UTC", datetime(2024, 10, 29, 13, 10, tzinfo=UTC)),
+        (date(2024, 11, 16), None, date(2024, 11, 16)),
+        (datetime(2024, 10, 29, 13, 10), "Asia/Singapore", datetime(2024, 10, 29, 5, 10, tzinfo=UTC)),
+        (datetime(2024, 10, 29, 13, 20), None, datetime(2024, 10, 29, 13, 20)),
+    ]
+)
+def test_can_complete_relative_calculation(alarms, dtend, timezone, trigger, tzp):
+    """The start is given and required."""
+    start = (dtend if timezone is None else tzp.localize(dtend, timezone))
+    alarms = Alarms(alarms.rfc_5545_end)
+    alarms.set_end(start)
+    assert len(alarms.times) == 1
+    time = alarms.times[0]
+    expected_trigger = normalize_pytz(trigger - timedelta(days=2))
+    assert time.trigger == expected_trigger
+
+
+@pytest.mark.parametrize("dtend", [date(1998, 10, 1), date(2023, 12, 31)])
+def test_end_as_date_with_delta_as_date_stays_date(alarms, dtend):
+    """If we have an alarm with a day delta and the event is a day event, we should stay as a date."""
+    a = Alarms(alarms.rfc_5545_end)
+    a.set_end(dtend)
+    assert len(a.times) == 1
+    assert a.times[0].trigger == dtend - timedelta(days=2)
+
+
+
+def test_add_multiple_alarms(alarms):
+    """We can add multiple alarms."""
+    a = Alarms()
+    a.add_alarm(alarms.start_date)
+    a.add_alarm(alarms.rfc_5545_end)
+    a.add_alarm(alarms.rfc_5545_absolute_alarm_example)
+    with pytest.raises(IncompleteAlarmInformation):
+        a.times  # noqa: B018
+    a.set_start(datetime(2012, 3, 5))
+    with pytest.raises(IncompleteAlarmInformation):
+        a.times  # noqa: B018
+    a.set_end(datetime(2012, 3, 5))
+    assert len(a.times) == 7
+
+
+def test_alarms_from_event_have_right_times(calendars):
+    """We can collect from an event."""
+    event = calendars.alarm_etar_future.subcomponents[-1]
+    a = Alarms(event)
+    assert len(a.times) == 3
+    assert a.times[0].parent == event
+
+
+def test_cannot_set_the_event_twice(calendars):
+    """We cannot set an event twice. This make the state ambiguous."""
+    event = calendars.alarm_etar_future.subcomponents[-1]
+    a = Alarms()
+    a.add_component(event)
+    a.add_component(event)  # same component is ok
+    with pytest.raises(ValueError):
+        a.add_component(calendars.alarm_google_future.subcomponents[-1])
+
+
+@pytest.mark.parametrize(
+    ("calendar", "index", "count", "message"),
+    [
+        ("alarm_etar_future", -1, 3, "Etar (1): we just created the alarm"),
+        ("alarm_etar_notification", -1, 2, "Etar (2): the notification popped up"),
+        ("alarm_etar_notification_clicked", -1, 0, "Etar (3): the notification was dismissed"),  # TODO: check that that is really true
+        ("alarm_google_future", -1, 4, "Google (1): we just created the event with alarms"),
+        ("alarm_google_acknowledged", -1, 2, "Google (2): 2 alarms happened at the same time"),
+        ("alarm_thunderbird_future", -1, 2, "Thunderbird (1.1): 2 alarms are set"),
+        ("alarm_thunderbird_snoozed_until_1457", -1, 2, "Thunderbird (1.2): 2 alarms are snoozed to another time"),
+        ("alarm_thunderbird_closed", -1, 0, "Thunderbird (1.3): all alarms are dismissed (closed)"),
+        ("alarm_thunderbird_2_future", -1, 2, "Thunderbird (2.1): 2 alarms active"),
+        ("alarm_thunderbird_2_notification_popped_up", -1, 2, "Thunderbird (2.2): one alarm popped up as a notification"),
+        ("alarm_thunderbird_2_notification_5_min_postponed", -1, 2, "Thunderbird (2.3): 1 alarm active and one postponed by 5 minutes"),
+        ("alarm_thunderbird_2_notification_5_min_postponed_and_popped_up", -1, 2, "Thunderbird (2.4): 1 alarm active and one postponed by 5 minutes and now popped up"),
+        ("alarm_thunderbird_2_notification_5_min_postponed_and_closed", -1, 1, "Thunderbird (2.5): 1 alarm active and one postponed by 5 minutes and is now acknowledged"),
+    ]
+)
+def test_number_of_active_alarms_from_calendar_software(calendars, calendar, index, count, message):
+    """Check that we extract calculate the correct amount of active alarms."""
+    event = calendars[calendar].subcomponents[index]
+    a = Alarms(event)
+    active_alarms = a.active  # We do not need to pass a timezone because the events have a timezone
+    assert len(active_alarms) == count, f"{message} - I expect {count} alarms active but got {len(active_alarms)}."
+
+
+three_alarms = Alarm()
+three_alarms.REPEAT = 2
+three_alarms.add("DURATION", timedelta(hours=1)) # 2 hours & 1 hour before
+three_alarms.add("TRIGGER", -timedelta(hours=3)) # 3 hours before
+
+
+@pytest.mark.parametrize(
+    ("start", "acknowledged", "timezone", "count"),
+    [
+        (datetime(2024, 10, 10), datetime(2024, 10, 9), "UTC", 3),
+        (datetime(2024, 10, 10, 12), datetime(2024, 10, 10, 9, 1), "UTC", 2),
+        (datetime(2024, 10, 10, 12), datetime(2024, 10, 10, 10, 1), "UTC", 1),
+        (datetime(2024, 10, 10, 12), datetime(2024, 10, 10, 11, 1), "UTC", 0),
+        (datetime(2024, 10, 10, 12, tzinfo=timezone.utc), datetime(2024, 10, 10, 11, 1), None, 0),
+    ]
+)
+def test_number_of_active_alarms_with_moving_time(start, acknowledged, count, tzp, timezone):
+    """Check how many alarms are active after a time they are acknowledged."""
+    a = Alarms()
+    a.add_alarm(three_alarms)
+    a.set_start(start)
+    a.set_local_timezone(timezone)
+    a.acknowledge_until(tzp.localize_utc(acknowledged))
+    active = a.active
+    assert len(active) == count
+
+
+def test_incomplete_alarm_information_for_active_state(tzp):
+    """Make sure we throw the right error."""
+    a = Alarms()
+    a.add_alarm(three_alarms)
+    a.set_start(date(2017, 12, 1))
+    a.acknowledge_until(tzp.localize_utc(datetime(2012, 10, 10, 12)))
+    with pytest.raises(IncompleteAlarmInformation) as e:
+        a.active  # noqa: B018
+    assert e.value.args[0] == f"A local timezone is required to check if the alarm is still active. Use Alarms.{Alarms.set_local_timezone.__name__}()."
+
+
+@pytest.mark.parametrize(
+    "calendar_name",
+    [
+        "alarm_etar_future",
+        "alarm_google_acknowledged",
+        "alarm_thunderbird_closed",
+        "alarm_thunderbird_future",
+        "alarm_thunderbird_snoozed_until_1457",
+    ]
+)
+def test_thunderbird_recognition(calendars, calendar_name):
+    """Check if we correctly discover Thunderbird's alarm algorithm."""
+    calendar = calendars[calendar_name]
+    event = calendar.subcomponents[-1]
+    assert isinstance(event, Event)
+    assert event.is_thunderbird() == ("thunderbird" in calendar_name)
+
+
+@pytest.mark.parametrize(
+    "snooze",
+    [
+        datetime(2012, 10, 10, 11, 1), # before everything
+        datetime(2017, 12, 1, 10, 1),
+        datetime(2017, 12, 1, 11, 1),
+        datetime(2017, 12, 1, 12, 1),
+        datetime(2017, 12, 1, 13, 1), # snooze until after the start of the event
+    ]
+)
+def test_snoozed_alarm_has_trigger_at_snooze_time(tzp, snooze):
+    """When an alarm is snoozed, it pops up after the snooze time."""
+    a = Alarms()
+    a.add_alarm(three_alarms)
+    a.set_start(datetime(2017, 12, 1, 13))
+    a.set_local_timezone("UTC")
+    snooze_utc = tzp.localize_utc(snooze)
+    a.snooze_until(snooze_utc)
+    active = a.active
+    assert len(active) == 3
+    for alarm in active:
+        assert alarm.trigger >= snooze_utc
+
+
+@pytest.mark.parametrize(
+    ("event_index", "alarm_times"),
+    [
+        # Assume that we have the following event with an alarm set to trigger 15 minutes before the meeting:
+        (1, ("20210302T101500",)),
+        # When the alarm is triggered, the user decides to "snooze" it for 5 minutes.
+        # The client acknowledges the original alarm and creates a new "snooze"
+        # alarm as a sibling of, and relates it to, the original alarm (note that
+        # both occurrences of "VALARM" reside within the same "parent" VEVENT):
+        (2, ("20210302T102000",)),
+        # When the "snooze" alarm is triggered, the user decides to "snooze" it
+        # again for an additional 5 minutes. The client once again acknowledges
+        # the original alarm, removes the triggered "snooze" alarm, and creates another
+        # new "snooze" alarm as a sibling of, and relates it to, the original alarm
+        # (note the different UID for the new "snooze" alarm):
+        (3, ("20210302T102500",)),
+        # When the second "snooze" alarm is triggered, the user decides to dismiss it.
+        # The client acknowledges both the original alarm and the second "snooze" alarm:
+        (4, ()),
+    ]
+)
+def test_rfc_9074_alarm_times(events, event_index, alarm_times):
+    """Test the examples from the RFC and their timing.
+
+    Add times use America/New_York as timezone.
+    """
+    a = events[f"rfc_9074_example_{event_index}"].alarms
+    assert len(a.active) == len(alarm_times)
+    expected_alarm_times = {vDatetime.from_ical(t, "America/New_York") for t in alarm_times}
+    computed_alarm_times = {alarm.trigger for alarm in a.active}
+    assert expected_alarm_times == computed_alarm_times
+
+
+def test_set_to_None():
+    """acknowledge_until, snooze_until, set_local_timezone."""
+    a = Alarms()
+    a.set_start(None)
+    a.set_end(None)
+    a.set_local_timezone(None)
+    a.acknowledge_until(None)
+    a.snooze_until(None)
+    assert vars(a) == vars(Alarms())
\ No newline at end of file
diff --git a/src/icalendar/tests/test_pytz_zoneinfo_integration.py b/src/icalendar/tests/test_pytz_zoneinfo_integration.py
index a02aa10d..c93735e7 100644
--- a/src/icalendar/tests/test_pytz_zoneinfo_integration.py
+++ b/src/icalendar/tests/test_pytz_zoneinfo_integration.py
@@ -90,3 +90,15 @@ def test_cache_is_emptied_when_tzp_is_switched(tzp, timezones, new_tzp_name):
     tzp.cache_timezone_component(timezones.pacific_fiji)
     tz2 = tzp.timezone("custom_Pacific/Fiji")
     assert tz1 is not tz2
+
+
+def test_invalid_name(tzp):
+    """Check that the provider name is OK."""
+    provider = "invalid_provider"
+    with pytest.raises(ValueError) as e:
+        tzp.use(provider)
+    # f"Unknown provider {provider}. Use 'pytz' or 'zoneinfo'."
+    message = e.value.args[0]
+    assert f"Unknown provider {provider}." in message
+    assert "zoneinfo" in message
+    assert "pytz" in message
diff --git a/src/icalendar/timezone/__init__.py b/src/icalendar/timezone/__init__.py
index dc751808..e0da7837 100644
--- a/src/icalendar/timezone/__init__.py
+++ b/src/icalendar/timezone/__init__.py
@@ -7,8 +7,10 @@ def use_pytz():
     """Use pytz as the implementation that looks up and creates timezones."""
     tzp.use_pytz()
 
+
 def use_zoneinfo():
     """Use zoneinfo as the implementation that looks up and creates timezones."""
     tzp.use_zoneinfo()
 
+
 __all__ = ["tzp", "use_pytz", "use_zoneinfo"]
diff --git a/src/icalendar/timezone/tzp.py b/src/icalendar/timezone/tzp.py
index 48cc1e4b..6c24b389 100644
--- a/src/icalendar/timezone/tzp.py
+++ b/src/icalendar/timezone/tzp.py
@@ -1,12 +1,19 @@
 from __future__ import annotations
-import datetime
-from .. import cal
-from typing import Optional, Union
+
+from typing import TYPE_CHECKING, Optional, Union
+
+from icalendar.tools import to_datetime
+
 from .windows_to_olson import WINDOWS_TO_OLSON
-from .provider import TZProvider
-from icalendar import prop
-from dateutil.rrule import rrule
 
+if TYPE_CHECKING:
+    import datetime
+
+    from dateutil.rrule import rrule
+
+    from icalendar import cal, prop
+
+    from .provider import TZProvider
 
 DEFAULT_TIMEZONE_PROVIDER = "zoneinfo"
 
@@ -41,10 +48,10 @@ def _use(self, provider:TZProvider) -> None:
     def use(self, provider:Union[str, TZProvider]):
         """Switch to a different timezone provider."""
         if isinstance(provider, str):
-            provider = getattr(self, f"use_{provider}", None)
-            if provider is None:
-                raise ValueError(f"Unknown provider {provider_name}. Use 'pytz' or 'zoneinfo'.")
-            provider()
+            use_provider = getattr(self, f"use_{provider}", None)
+            if use_provider is None:
+                raise ValueError(f"Unknown provider {provider}. Use 'pytz' or 'zoneinfo'.")
+            use_provider()
         else:
             self._use(provider)
 
@@ -52,20 +59,20 @@ def use_default(self):
         """Use the default timezone provider."""
         self.use(DEFAULT_TIMEZONE_PROVIDER)
 
-    def localize_utc(self, dt: datetime.datetime) -> datetime.datetime:
+    def localize_utc(self, dt: datetime.date) -> datetime.datetime:
         """Return the datetime in UTC.
 
         If the datetime has no timezone, set UTC as its timezone.
         """
-        return self.__provider.localize_utc(dt)
+        return self.__provider.localize_utc(to_datetime(dt))
 
-    def localize(self, dt: datetime.datetime, tz: Union[datetime.tzinfo, str]) -> datetime.datetime:
+    def localize(self, dt: datetime.date, tz: Union[datetime.tzinfo, str]) -> datetime.datetime:
         """Localize a datetime to a timezone."""
         if isinstance(tz, str):
             tz = self.timezone(tz)
-        return self.__provider.localize(dt, tz)
+        return self.__provider.localize(to_datetime(dt), tz)
 
-    def cache_timezone_component(self, timezone_component: cal.VTIMEZONE) -> None:
+    def cache_timezone_component(self, timezone_component: cal.Timezone) -> None:
         """Cache the timezone that is created from a timezone component
         if it is not already known.
 
diff --git a/src/icalendar/tools.py b/src/icalendar/tools.py
index 896aa7a6..b8b2f7f2 100644
--- a/src/icalendar/tools.py
+++ b/src/icalendar/tools.py
@@ -1,11 +1,9 @@
-from datetime import datetime
-from icalendar.parser_tools import to_unicode
-from icalendar.prop import vDatetime
-from icalendar.prop import vText
-from string import ascii_letters
-from string import digits
-
+from __future__ import annotations
 import random
+from datetime import date, datetime, tzinfo
+from string import ascii_letters, digits
+
+from icalendar.parser_tools import to_unicode
 
 
 class UIDGenerator:
@@ -18,18 +16,58 @@ class UIDGenerator:
     def rnd_string(length=16):
         """Generates a string with random characters of length.
         """
-        return ''.join([random.choice(UIDGenerator.chars) for _ in range(length)])
+        return "".join([random.choice(UIDGenerator.chars) for _ in range(length)])
 
     @staticmethod
-    def uid(host_name='example.com', unique=''):
+    def uid(host_name="example.com", unique=""):
         """Generates a unique id consisting of:
             datetime-uniquevalue@host.
         Like:
             20050105T225746Z-HKtJMqUgdO0jDUwm@example.com
         """
+        from icalendar.prop import vDatetime, vText
         host_name = to_unicode(host_name)
         unique = unique or UIDGenerator.rnd_string()
         today = to_unicode(vDatetime(datetime.today()).to_ical())
-        return vText(f'{today}-{unique}@{host_name}')
+        return vText(f"{today}-{unique}@{host_name}")
+
+
+def is_date(dt: date) -> bool:
+    """Whether this is a date and not a datetime."""
+    return isinstance(dt, date) and not isinstance(dt, datetime)
+
+
+def is_datetime(dt: date) -> bool:
+    """Whether this is a date and not a datetime."""
+    return isinstance(dt, datetime)
+
+
+def to_datetime(dt: date) -> datetime:
+    """Make sure we have a datetime, not a date."""
+    if is_date(dt):
+        return datetime(dt.year, dt.month, dt.day)  # noqa: DTZ001
+    return dt
+
+
+def is_pytz(tz: tzinfo):
+    """Whether the timezone requires localize() and normalize()."""
+    return hasattr(tz, "localize")
+
+
+def is_pytz_dt(dt: date):
+    """Whether the time requires localize() and normalize()."""
+    return is_datetime(dt) and is_pytz(dt.tzinfo)
+
+
+def normalize_pytz(dt: date):
+    """We have to normalize the time after a calculation if we use pytz.
+
+    pytz requires this function to be used in order to correctly calculate the
+    timezone's offset after calculations.
+    """
+    if is_pytz_dt(dt):
+        return dt.tzinfo.normalize(dt)
+    return dt
+
 
-__all__ = ["UIDGenerator"]
+__all__ = ["UIDGenerator", "is_date", "is_datetime", "to_datetime", "is_pytz", "is_pytz_dt", "normalize_pytz"]