I have to find the time period for 12 months prior and 12 months after a certain instance.

For example, if the instance happened in June 2005, the prior 12 months are June 2004 to May 2005 and the post 12 months are July 2005 to June 2006.

The date arithmetic I use is as follows:

If my date is in B2,
the prior period is from

=DATE(Year(b2),month(b2)-12,day(b2) to =date(year(b2),month(b2)-1,day(b2))

It works great except, due the fact that the day is included in the calculation, it moves over to the prior or next month sometimes, if the date of my instance is >15th of a month (You know what I mean)

I don't care about the day, all I care about is the month. How can I eliminate the effect of the day in this calculation?

Thanks,
xix