I'm impressed, Art. I thought it was only dinosaur computer programmers like me who would easily guess that. I just caught myself short in the midst of typing a reply guessing the same thing about 1969 and UNIX time, but in a lot more words of course. No surprise with Jarrod's background in the UNIX-based computer world.

Some might think events in the known universe should be stored numerically with time zero being the Big Bang. For the UNIX developers at Bell Labs in the 1970s, they decided their universe began at time zero, called the UNIX epoch date, being 1 January 1970 00:00:00 UT (GMT). That date was convenient for them to use since the current internal system date could then be easily stored as a small 16-bit or 32-bit number and there were no UNIX based computers prior to 1970. Now fortunately for those UNIX developers, a modern 64-bit computer can now easily store an event time as a signed integer in seconds before or after the UNIX epoch right back to the current estimated Big Bang.

As you note, the year 1969 will display when the zero epoch is displayed as local time for more westerly time zones still in the previous year. Also, in Greenwich, the zero epoch when displayed in normal 12 hour format is 12:00AM December 31st, 1969. Way back in the day when I was debugging programs, whenever chasing an erroneous year displayed as 1969, the first thing you would go looking for was a zero missing date.

As for the non-UNIX world, Windows based computers often store date/time stamps as the number of 100-nanosecond ticks since 1 January 1601 00:00:00 UT. For general computational purposes in terms of days, the computer world has long used Julian dates, being the number of days since January 1, 4713 BC, the beginning of Julius Caesar's calendar.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now