I just discovered that DateDiff can give you a wrong answer if you were expecting what I was, so I wanted share it.
If you have Date1 = #12/31/2003# and Date2 = #1/1/2004#, then
Int((Date2 - Date1) / 365.25) = 0
DateDiff("yyyy", Date1, Date2) = 1
I thought this was a bug because clearly only one day has passed so the DateDiff should return zero also. But in the DateDiff help it says:
quote:When comparing December 31 to January 1 of the immediately succeeding year, DateDiff for Year ("yyyy") returns 1 even though only a day has elapsed.
I also noticed that counting months and weeks ("m" and "ww", respectively) are wrong, too.
This is terrible... DateDiff should return the true number of months and years elapsed, not just subtract the month or year parts from each other!
Michigan Dept. of Environmental Quality, Air Quality Division