Delimiter character isn't the correct one for the delimiter's position in the string

The fully-formatted error message

An unexpected delimiter, '?', was encountered after the 'day-of-month' digits ('29'):

          1992-05-29?12:25:12.1-01:00
                  ^^X

A 'T' belongs in that position.

Substitutions

Name	Value	Type	Source
Input	1992-05-29?12:25:12.1-01:00	String	The ISO8601 string being parsed
Expected	'T'	Char	What the parse command is looking for
Actual	'?'	Char	What the parse found
PreviousName	"day-of-month"	String	The name of the field immediately preceding the erroneous delimiter
PreviousValue	29	String or Int	The value of the immediately preceding field
PreviousType	digits	String	"digits" or "delimiter"
PreviousStartOffset	9	Int	The displacement from the start of the string being parsed to locate the leftmost '^'
PreviousCharCount	2	Int	The number of '^' chars to position under the previous value
TopLine	"An unexpected delimiter, '?', was encountered after the '?' digits (?):"	String	This error category
BottomLine	"A '?' belongs in that position."	String	This error category

Notes

1. The Value column above describes the example values in the sample error message above.
2. The offset of the actual error position is calculated: it is always after the sum of the PreviousStartOffset and the PreviousCharCount.
3. Here the number of 'X' is one. But Digit sequence has wrong length has no 'X' because the error field is the first one.
4. Note that TopLine and BottomLine have '?' marking where values will be substituted.
5. I'm wondering if the type of the preceding field can be automatically derived.