I'm using the DateDiff to calculate various values. I've got everything to work. However I don't know what influence the firstweekofyear has on a calculation. Whatever value I try i.e. 1,2 or 3 I get the same answer. However further in the future I may have a problem because I don't know what affect the firstweekofyear could have.

Can anyone give me an example where changing the firstweekofyear value gives me a different answer.

While I'm on the subject, what is the difference in using the "d" interval symbol as opposed to the "y" symbol.

Well, the first week of year issue is only going to matter if your interval is weeks....I think...determines what gets counted as a "week" during the turn of the year. I thihk if you have the setting that says Jan1 starts a new year and week, you might end up with an extra week if you're counting the weeks between Dec 15 and Jan 30, say. But if you're counting days, can't see what diff that setting would make.

As for the difference between y and d, no clue...might be an old functionality they kept for backwards compatibility that no longer does anything??

Ben

From Access Help files .....

firstdayofweek:
Optional. A constant that specifies the first day of the week. If not specified, Sunday is assumed.

firstweekofyear:
Optional. A constant that specifies the first week of the year. If not specified, the first week is assumed to be the week in which January 1 occurs.

RDH