Cannot group by date in a pivot table

[MCVCOTE]

I get an message saying I cannot group on that selection.

 

[Dave Peterson]

The values in that field have to be all numeric--they can't even be
blanks/empty.

 

[MCVCOTE]

The field itself is a date and each entry does have a date. I've grouped on
it before but can no longer do it. I've tried refreshing, updating the data,
and nothing seems to work. It brought in the data on a daily basis and I'm
trying to group it by month instead.

 

[Debra Dalgleish]

There may be a left over field from a previous grouping. There are
instructions here on how to fix the problem:

http://www.contextures.com/xlPivot07.html#Problems