How can I calculate the number of hours between two dates?
The best way to do it (and the fastest) is to do it in the database. If you simply subtract the two days, you will get a number in the format D.T, where “D” is the number of days, and “T” is the fraction of days in decimal form. In other words, day 2 and noon minus day 1 at midnight will yield 1.5 as the result.
Take this number and multiply by 24, that gives you the number of hours. Take the decimal portion of that and divide by 60 and you get the number of minutes. So if you have 1.5 (earlier example) and multiply by 24 you get 36 hours and 0 minutes.
Cindy Clayton 
(BOB member since 2002-06-11)