Kirill Bondar 2/26/2021 6:27:09 AM
MonthsBetween(end, start) counts the number of "1st of the month" between two dates. BTW, same behavior is exposed by QuartersBetween() and YearsBetween().
To match DATEDIF behavior you simply need to subtract 1 from result if ends date's day of the month is less then start date's day of the month.
MonthsBetween([End], [Start]) - If(Day([End]) < Day([Start]), 1)