3 ms·

And the leap seconds meaningfully alter that?

• lutorm 7y ago
  Yes. Leap seconds are there to align UTC (an atomic time) with UT1, which is defined based on mean solar time, ie "the day", since UT1 isn't uniform. Without leap seconds, UTC will slowly drift out of sync with the Earth's rotation.
  • ergothus 7y ago
    That's the point though. The above post said leap seconds cause more harm than good - a correction done once a century would fit well enough within the purpose you've defined here. If UTC is out of sync with the sun by less than a minute, no human will notice, and non-humans don't care about the sun and are happier with fewer disruptions.