There may be a grouped field left over from the previous time that you
grouped the data. Check the field list, to see if there's a second copy
of the date field, e.g. Date2.

If there is, add it to the row area, and ungroup it.

Then, you should be able to group the date field again.

wrote:
I am trying to group a column of dates by year and month, and I've done
it before and it's worked fine. But now it's saying "Cannot group on
that Selection". I checked the data and it's in date format and there
aren't any blank or null values. It seems like this is a bug because
I've done it before with the same exact data. Have any of you had this
problem? What am I doing wrong?


--
Debra Dalgleish
Excel FAQ, Tips & Book List
http://www.contextures.com/tiptech.html