Base CC expiry on the rails configured timezone

I'd rather `rm -Rf` all timezones worldwide, but the UN isn't accepting pull
requests.

Apparently ActiveSupport's .to_time doesn't respect the rails configured 
timezone and instead uses the system's local timezone. This would cause the CC
to expire early in positive timezones or later for negative offset timezones.

This is not a big issue in production (processors will reject expired cards
anyways and customers shouldn't be too upset about nearly expired cards), but
it lets my tests pass at 11pm on the 30th.