The DateDiff function will tell you the difference between two times. The
DateAdd will let you add a number of seconds or minutes or hours to a time.
From what you're describing, though, it sounds as though your time fields
are durations: that 9:30 means 9 hours and 30 minutes, not the time nine
thirty. You should know that there isn't a Time data type in Access: the
Date/Time data type is intended for a timestamp, not a duration (under the
covers, it stores the values as an 8 byte floating point number, where the
integer portion represents the date as the number of days relative to 30
Dec, 1899, and the decimal portion represents the time as a fraction of a
day)
If you have just a time, the date portion is set to 0. However, if you add
times together, you'll eventually exceed 24 hours, so that suddenly you'll
have a date. For example, 6:00 is .25 (a quarter of a day), and 8:00 is
..33333 (a third of a day). If you add 8:00 + 8:00 + 6:00 + 6:00, you'll have
1.16667. Rather than being 28:00 as you'd expect, it'll only show 2:00
Realistically, durations should be stored in a numeric field, not a
date/time field.
