You need to have a date/time in A1 - for example, enter 8/01/07 13:00
in this cell and use Format | Cells | Number (tab) | Custom and set the
format as ddd hh:mm.

Then in A2 enter this formula:

=A1 + 0.5

The format should be the same as A1. Excel treats times as fractions of
a 24-hour day, which is why you need to add 0.5.

Hope this helps.

Pete

Alexander wrote:

Dear all,

If A1 is equal to Mon 1300, and when I plus another 12hrs in A2, it will
become Tue 0100 in A2.

Any idea how to achieve this?

Thanks!