User blog comment:Withersoul 235/My Problems With UCP/@comment-45254201-20200827083736/@comment-26939652-20200830071724

January 1st 1970 is the start of the computer age, also referred to as the Unix epoch. This is typical for conversions that force the end result to a number by returning 0 if conversion fails. Zero corresponds to January 1st, 1970 00:00:00.

We can all blame this on php/mysql-isms in the late 1990's / early 2000's, because php didn't have a proper timestamp type, but instead internally used the unix epoch and MySQL provided non-standard conversion functions  and   to accommodate php.

The 1969 version is exactly the same, but for timezones that are negative UTC - for them, midnight January 1st is still 1 or more hours away and thus it's still 1969.