Love this article, but one thing it skipped on was more in-depth on Leap Seconds.
You see, UTC, is kinda like another human-made-up timezone. Humans made up some rules, and UTC is a 37 second offset from TAI / International Atomic Time:
You see, UTC, is kinda like another human-made-up timezone. Humans made up some rules, and UTC is a 37 second offset from TAI / International Atomic Time:
Like most things associated with time Leap Seconds are a huge headache to implement properly on computers. If you want some fun watch what various NTP servers around the world do when Leap Seconds roll around. You will see clocks that start to drift for 15 minutes before jumping to the right time, some that wait until 8AM local time on the following day to correct, and some that just go crazy. And of course you have Google's clock smearing across most of a day.
IIRC there was one major earthquake that caused a sooner than expected Leap Second adjustment.
Fun fact: GPS, NTP, and many similar timing formats have flags in the signal that warn clients of upcoming leap second events. Few receivers pay attention to them however.
As a note, clock smearing is a non-standard hack invented by Google, because most programs are too broken to handle the leap second warning event and inserting/deleting a second properly, per designed. And you shall never add a clock smearing server to the www.pool.ntp.org.
But internal changes in the Earth can also cause changes in the rotation period. For instance the 2011 Tohoku earthquake shortened the day by 1.8 us [1].
[1] https://www.earthobservatory.sg/blog/how-did-2011-tohoku-ear...
Note that if the day slows by 5.5 ms from 24 hours, then we need an average of more than one leap second per 6 months to keep up. Per https://en.wikipedia.org/wiki/Earth%27s_rotation the Earth's rotation changed by 1.7 ms in the last century, an average of 2.3 ms in last thousand, and it is being affected by a variety of causes right now.