Manual adjustment of Hijri Calendar

[hafizmdyasir]

Since Hijri calendar is lunar, calculations performed well in advance never hold up. This is just the way lunar cycles work and there is no way around that.
However, there should be a way in the calendar to manually adjust it by a couple of days or so such that after adjustment, the calendar is in accordance with the latest information.

For instance, hijriCalendar.adjust(+2) should make it so that 2 Muharram corresponded to 2 July originally, it should now correspond to 4 July instead. (or something similar).

This is an essential part that is missing fron almost all implementations of the Hijri calendar system so far.