Problem Statement

Choose popular date libraries used by your language and show the   epoch   those libraries use. A demonstration is preferable   (e.g. setting the internal representation of the date to 0 ms/ns/etc.,   or another way that will still show the epoch even if it is changed behind the scenes by the implementers),   but text from (with links to) documentation is also acceptable where a demonstration is impossible/impractical. For consistency's sake, show the date in UTC time where possible.

Let's start with the solution:

object cal = Calendar.ISO->set_timezone("UTC");
write( cal.Second(0)->format_iso_short() );