Lasma wants her pivot table to group daily dates up to months and years. But she has some empty rows and the Group Field is greyed out.

In this video:
Surprise! Microsoft 365 now allows blanks in the date field and you can still group.
Solution 1: Fill blank date fields with 2199 December 31
Solution 2: Add your own Year and Month fields to the data set
And, a warning from Debra Dalgleish at Contextures: if you mix dates and text, the Group Field will still be greyed out.

Table of Contents
(0:00) Pivot Group Dates with Blanks
(0:15) Fix from Excel Team
(1:10) Select empty date cells
(2:09) Add Year Month to source data
(2:40) Month Name from date using TEXT
(3:30) Debra: mix of dates and text
(4:00) “empty” cells by spacing through
(4:48) Wrap-up