https://factorio.com/blog/post/fff-388 - they wanted to use a 64 bit int for the tick count, but Lua doesn't have one; so they used the one available and worked out when it would lose precision.

"More than 2 million years seems to be enough for us to not be around any more when the bug reports start appearing."

I once saw a pop-up in a game saying something along the lines of: wow, it's 10 years later and this game is still being played! Made me laugh out loud, nice little easter egg.

Sadly, I don't recall which game it was. Maybe SpaceChem?