All dates and time is stored in UTC, when the user comes to the site I see its time zone (indicates when the check-in) and translate the date and time in the user timezone. There is nothing complicated.
The problem is this:
There are events where it is all day, then he has no time. Those dates I keep this: 2016-11-14 00:00:00, another field "allday" flag of 0 or 1.
And I don't know how to translate them?