According to Ruby, the world ends – or at least gets seriously reshuffled – on Tuesday the 19th of January 2038, at 7 seconds past 3:14 AM UTC.
>> Time.utc(2038, 1, 19, 3, 14, 7, 999999)
=> Tue Jan 19 03:14:07 UTC 2038
>> Time.utc(2038, 1, 19, 3, 14, 7, 999999).succ
=> Fri Dec 13 20:45:52 UTC 1901
One second after that moment, and we’re back in 1901. Surprise!
This is the classic Year 2038 problem – time is stored as a signed 32-bit integer counting seconds from the Unix epoch, and that integer overflows right at this boundary.
What’s a bit surprising is that Ruby doesn’t handle this more gracefully. A Fixnum automatically promotes to a Bignum when it exceeds 2**30, so you might expect Time to pull off a similar trick internally. But it doesn’t – at least not in the Ruby versions of this era. The internal representation just wraps around, catapulting you back to the early 20th century without so much as a warning.
Something to keep in mind if you’re ever working with dates far into the future.