From a favourite Reddit thread:

- Why in the hell would a date value-- particularly one that's an offset-- be signed?

- - How were you planning on indicating dates prior to 1970-01-01?

- - - What date before 1970? We just all assume those do not exist.

- - - - "Now you've made me feel old." "How old are you?" "Let me put it this way: when I was born, time didn't exist."

https://old.reddit.com/r/programming/comments/2b4kpg/conspir...

The full context is ... kind of fun:

https://old.reddit.com/r/programming/comments/2b4kpg/conspir...

Well if we bite the bullet and use a 512 bit unsigned int we can represent time zero as the Big Bang and we should be good until the heat death of the universe, based on my napkin math. But I'm no physicist or kernel contributor so unsure of the implications.

No way. Do we know exactly when big bang was or that a second has always been a second since then?

We don't want time implementations based on some definition of big bang version 1.1.3 and all other versions as physicians change the definition of time since big bang.

If the big rip theory is correct, then 64 bits will suffice.

What happens when we revise the moment of the Big Bang? Maybe need signed 1024 bit just in case.

Might as well just make it signed at that point. We'll never need more than kilibit to represent time.

Instead we now assume dates past 2038 don't exist...

Time is an illusion.

Lunchtime doubly so.

Huh, just realized - time ends at pi-o'clock.

This is how I usually compute pi.

I would bet they were more confident someone would want to represent data from the recent past than that someone would still be using their research lab OS in 60 years.

Well, now we should use 64-bit timestamps, and 64-bit timestamps is I think sensible to be signed, since there shouldn't need a reason for unsigned 64-bit timestamps.

“In 30 years from now everything will probably be 512 bit and flying cars, right?”

That’s the wrong thing. It’s not “will this computer still be running” it’s “does the life of this format work over the time people will use it”. If in 2000 we had 512bit and flying cars, Unix epoch still could be the standard.

The first epoch seconds computers aren’t running things anymore. But, it lives on as a standard.

So the issue isn’t “was it a good idea to count seconds starting at 1970”, but rather “why the hell would anyone use signed for a value that can only be positive? ... and then keep doing it once they realized the problem!?”

2105 or 2106 wont be an issue for unsigned. No one will use a 32bit standard much longer let alone in the 30 years leading up to the problem date.