In cells H15 and H36 I have 10/31/09 and 1/31/10 respectively.
In J 15 and J36 I have the following formula:

=DATE(YEAR(H15),MONTH(H15-DAY(H15))+2,)
Cell J36 has With H36 instead of H15.
The intent is to identify the last date of the month identified in column H.

However, the results a
H J
10/31/09 10/31/09 (This worked)
1/31/10 1/31/11 (This added a whole year)

The equation seems to work every where unless the date in column H is in
January.

Column L does something similar to calculate the end of the subsequent
month. It works in all cases. The formula I used for that is:
=DATE(YEAR(H36),MONTH(H36-DAY(H36)+2)+2,)

Why isn't the first formula working in every case?

TIA

Papa J