If we eliminate leap seconds, we'll need a leap hour in ~500 years. It could be ...

throw0101c · 2026-03-09T19:11:35 1773083495

> It could be announced 50 years in advance.

Which is about how long it took for folks to switch from the Julian to the Gregorian calendar.

tmp10423288442 · 2026-03-09T20:38:12 1773088692

It took much longer than that, although to be fair the Catholic countries had switched in much sooner than 50 years.

wmf · 2026-03-09T20:32:52 1773088372

In the US DST was changed in 2005 and the change went into effect in 2007.