[0] https://gist.github.com/timvisee/fcda9bbdff88d45cc9061606b4b...
23:59:60 happens when we add leap seconds to the clock, for instance...
Daylight savings time is a much larger departure from this rule ;)
> 23:59:60 happens when we add leap seconds to the clock
Not anymore! Or, maybe not anymore. We've agreed to phase out leap seconds before 2035 [1] and we probably won't get a 23:59:60 before then [2].
[1] https://www.nature.com/articles/d41586-022-03783-5
[2] https://manifold.markets/Yev/will-there-be-another-positive-...
I read[0] that "It will take about 50,000 years for a mean solar day to lengthen by one second (at a rate of 2 ms per century)" and "The [accumulated] difference between UTC and UT would reach 0.5 hours after the year 2600 and 6.5 hours around 4600" which I expect will be sufficient to take us through to the time where we will no longer need co-ordinated time or an IERS.
[0] https://en.wikipedia.org/wiki/Coordinated_Universal_Time
Round-the-clock shiftwork (hospitals, power plants, etc.) will require minor tweaking; your eight hour shift probably just becomes 8:10 or so.
(It's worse for humans on Earth working Mars time, which is a thing that already happens. They come in 40 mins later every day. https://mars.nasa.gov/resources/20090/living-on-mars-time/)