datediff
Calculate the difference between two dates, returning a single part of that difference.
The filter takes a list with 2 parts [start, end] as date range argument.
The filter argument the “part” that will be extracted, and is one of Y, M, D, H, I, S.
Example, where start = 2012-02-02, end = 2012-03-01:
{{ [end, start]|datediff:"M" }}
Returns 1, since the difference in months between those 2 dates is 1.