I'm trying to create a new shifttime based on the original shifttime and
some overtime hours.
Let's say somebody works from 07:00 - 15:30 and is doing overtime from
15:30 - 16:30.
The new created shifttime should be displayed as 07:00 - 16:30.
Another example:
Original shift 14:00 - 22:00, overtime 12:00 - 14:00. New created
shifttime should be displayed as 12:00 - 22:00.

A similar question is when you take back some hours from the original
shifttime. For example, original shift 12:00 - 20:00, take back 18:00 -
20:00, new created shifttime should be displayed as 12:00 - 18:00.

Is there a function to accomplish that?

with kind regards,
Bert