Net change of facebook followers in 30 day period
I am trying to make a calculated field which determines the net change in facebook followers in the last 30 days. The data has columns:
Date: November 04, 2018 1:00:00 AM
Total Page Fans: 262
How can I determine the number of fans 30 days ago, and yesterday and output the difference for my card? I am very amateur at this logic so please try to be descriptive!