How to Think About Time in Programming

The way Google implemented leap seconds wasn't by sticking a 23:59:60 second at the end of 31st Dec. The way they did it was more interesting.

What they did instead was to "smear" it across the day, by adding 1 / 86400 seconds to every second on 31st Dec. 1/86400 seconds is well within the margin of error for NTP, so computers could carry on doing what they do without throwing errors.

Edit: They smeared it from noon before the leap second, to the noon after, i.e 31st Dec 12pm - 1st Jan 12pm.

RachelByTheBay wrote about doing that here:

http://rachelbythebay.com/w/2025/01/09/lag/

That was probably at Move Fast And Break Things Corp, instead of We Used To Be Do No Evil Inc.