Pivot Table - Group by Date Excel 2007

[evoxfan]

In my pivot table I tried to right click the "Date" column in order to group
by month.
A message popped up "Cannot Group that Selection".
Is there another way to group by month?
Should I create another column for month in my data source?

These are my headers for data source on another worksheet in the same
workbook.
PC# DATE PAYEE DESCRIPTION CHECK AMOUNT PHASE CODE

Thanks in advance for any help.

 

[evoxfan]

I found the error.
Some of the dates were blanks or the values in the amount column were blanks.
After correcting the data, the pivot table worked fine.