Handle date formats better amongst Pg and Sqlite

[flash548]

Seems theres some differences here - sqlite does the nice ISO8601 format whereas pg returns (at least through the app) without the ISO8601 'T' and 'Z' letters. This croaks in 'get_days_since_gmstamp' in the User Service.. rn I put in a simple if/else for the db type but needs a better implementation - and one that can handle some undef or exception case better.