On Mon, 10 Aug 2009 17:11:24 -0400, "T. Valko"
wrote:

If your times are true Excel times and you want to drop the seconds:

A1 = 6:19:21

=TIME(HOUR(A1),MINUTE(A1),0)-TIME(0,30,0)

Format as h:mm

This looks nicer than my proposal.
It can be a bit more compact, like this:

=TIME(HOUR(A1)+24,MINUTE(A1)-30,0)

The +24 is needed to be able to handle input before 00:30 AM.

Hope this helps / Lars-Åke