How to create loop for date addition?

Primarily the dates, the time boundary will need to update accordingly when a new date is set.

For example,
Initial PO1 03-Mar 08:00:00 to 05-Mar 08:00:00
then final outcome
PO1 03 Mar 08:00:00 to 03 Mar 24:00:00
PO1 04 Mar 00:00:00 to 04 Mar 24:00:00
PO 1 05 Mar 00:00:00 to 05 Mar 08:00:00