704 | Audit code to ensure all dates are stored in UTC

https://trello.com/c/TvXlpCUz/704-audit-code-to-ensure-all-dates-are-stored-in-utc

Currently dates are stored in database with local time zone.
This change causes that all dates are stored in UTC.

Change-Id: I525c45999ad6dee616753e868a09caf11552465a