Bottom line: never trust a spreadsheet. You're going to hear me say that a lot in this production! Especially when it comes to dates.
Postgres is pretty good at dealing with dates... in fact it's amazingly powerful as well as correct:
select now(); -- what date and time is it where my server is located?
select now() + '1 day' as tomorrow; -- adding an interval is extremely easy
select now() at time zone 'America/New_York'; -- specifying a timezone