Leap second and UT1-UTC information | NIST
Leap seconds have been inserted into our time system for a very long time.
Then there is this new twist: A global timekeeping problem postponed by global warming | Nature
The author asserts that negative leap seconds cannot be accommodated and will lead to a “Y2K” catastrophe, but from the NIST, they already appear to have both positive and negative adjustments to coordinated time, as the time standards are frequently updated in + or – tenths of a second.
