Conpherence - implement epoch creation slightly differently

Summary: D6114 fixed some bugs but on production it shows up as a new bug where Saturday is the first day? stop messing with the DateTime object so much and do some old school epoch manipulation. This works correctly on my laptop and my still fail in production, but it will rule out DateTime suckage.

Test Plan: still works on laptop

Reviewers: epriestley, chad

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D6115