Counts backwards 30 days starting from the most recent midnight. Partial days are not included. Can only be used as a range
parameter in for_date_range().
Syntax
last_30_days()
Example
If you view a column with the following function at 10 a.m. on October 31th, the function returns the number of clicks between October 1, 12:00 a.m. and October 30, 11:59 p.m.
Clicks.for_date_range(last_30_days())