The 0th day of one month is the last day of the previous month. For
example, if your date is 15-Jan-2009, the MONTH returns 1, so MONTH+1
is 2, and the 0th day of month 2 (February) is the last day of the
previous month (January).


Cordially,
Chip Pearson
Microsoft Most Valuable Professional
Excel Product Group, 1998 - 2009
Pearson Software Consulting, LLC
www.cpearson.com
(email on web site)

On Tue, 20 Jan 2009 05:50:31 -0800, WLMPilot
wrote:

I was given a formula for one of my questions a while back and I am trying to
understand what it is doing. Below is the formula:

=DATE(YEAR(A42),MONTH(A42)+1,0)

If A42 = 1/15/09, then the above formula returns 1/31/09. My two questions
a

1) Why doesn't MONTH(A42)+1 change the month to Feb?
2) What purpose does 0 in the day spot of DATE serve?

Thanks,
Les