Change start time and finish time (hours and minutes)

Hi All.

My query to end this week is the most difficult to resolve. I have  figured out the issue but failed to fix it.

My program is based on weeks and days, however when viewing the time (hours and minutes) format. My project start and finish links are inconsistent with time. I realised this when my durations didn't add up.

For eg. Ideally a 3 day duration- Start Monday, finish Wed evening. However my programme, 3 day duration. starts Monday, finishes midday Thursday.

The activities start and finish times are inconsistent i.e. start 0830, 10:00, 11:00 and finish 16:00, 17:30, 0830 (the following day).

The reason as to why it does this is it is a p6 export, that came with the dodgy times. When creating new programs the times are fine. However when copying and pasting chunks from the p6 export in to a new asta program the issue arises again.

Unfortunately, i can not redo the progrram as its 1800 activities long.

Is there an easy way to globally change the start and finish times, and locking the durations in place?

Thank you for your help.