How do I refer to the last day of a given date’s month? (I’m calculating the notice period in a contract.)
You need to use the special function
@last-day-of-month . See https://help.clausebase.com/kb/special-functions/#last-day-of-month6
For example, if you have a datafield
#contract^commencement-day , in which the current value happens to be 2nd February 2020, then
@last-day-of-month(#contract^commencement-day) will result in 29th February 220.