The type of the
todate in several methods is set to
unix epoch date, range [0, 253,402,300,799]
I don't know what that is and I can't find any information -- can someone explain it or point me to the right place?
These are Unix timestamps. They represent the number of seconds that have passed since the Unix Epoch, which occurred at 12:00 am UTC on January 1, 1970.
You can convert a human-readable date to / from a Unix timestamp using Wolfram Alpha. Example queries:
The end of the range is the highest possible date represented by as a timestamp.