This reduces the period of time that some of the unit tests
for calculate_next_automated_backup() are failing right now
(from 1week to just some hours around the DST changes).
Note it's not the final solution because they will still fail
when New_York or Brussels DST changes are about to happen, but
to get this completely fixed we'll need to wait to switch from
current custom TZ/DST support to PHP built-in one.
Eloy Lafuente (stronk7)