merged branch Seldaek/date_modify (PR #757)

merged branch Seldaek/date_modify (PR #757)

Commits
-------

ae85586 Add docs for date_modify
0366cf6 Fix docs of date filter

Discussion
----------

Date modify filter

This is probably possible via `date(foo)|modify('-1day')|format()`, but it's non obvious and a dedicated filter might be a bit more prominent.

---------------------------------------------------------------------------

by fabpot at 2012-06-22T07:01:32Z

Just a quick thought: As it modifies the date, it should probably be a function, not a filter.

---------------------------------------------------------------------------

by stof at 2012-06-22T07:24:52Z

@fabpot Aren't filters meant to transform the value ?