help how to crate group of date with Dynamic Range?

[Tiya]

Hi
I am useing Pivot Table to create data where i am useing Data,Party
Name,Group,Wt.,Rate,Amt.

In this Data i have given range name (database) with Dynamic Range
=OFFSET(Sheet1!$A$5,0,0,COUNTA(Sheet1!$A:$A),6)

But when i use Date in report i try to create Group of date in month or year
or day and qty it says can't create a gorup?

Any help how to crate group of date, with Dynamic Range?

Thanks

Tiya