The previous implementation interpreted the creation date as a local
time, and applied the rollover to that. If the initial creation date
was around midnight local time, even a one hour change due to daylight
savings could result in Anki skipping or doubling up on a day. To
address this, the rollover is now applied to the current time instead
of the creation date.
The new code needs the current time passed into it. This makes it
easier to unit test, and for AnkiWeb to be able to use the user's local
timezone.
The new timezone code is currently disabled, as this code needs to be
ported to all clients before it can be activated.
