Base CC expiry on the rails configured timezone

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.

Fixes #4632