5 ms·

A monotonic clock without leap seconds could be kept next to UTC, it can easily be standardized. The idea that this problem is so hard that users have to be in

A monotonic clock without leap seconds could be kept next to UTC, it can easily be standardized. The idea that this problem is so hard that users have to be inconvenienced to the point that reality is ignored is a bit strange to me.

dexwiz 4y ago
This is literally what the TIA standard is. Anything that needs precise time already uses this standard.
deleted 4y ago
[deleted]
adrian_b 4y ago
The problem is that UTC, despite its name, is not a time (it is an angle rounded to a multiple of 1/21600 right angles). Only TAI is a time. Already decades ago, some programmers have argued that internally all computers and their software should use only TAI, which is a time, so it behaves as expected, while UTC must be used exactly like the local times and the time zones, only at the interfaces with humans. If that proposal would have been adopted, there would not have been now any discussion about the leap second. The only reason for the existence of UTC is to keep dUT1, i.e. UT1 - UTC, under 1 second. If the leap second is eliminated, then dUT1 will grow over 1 second, so there are other cohorts of hardware devices and software applications that must be updated in order to no longer rely on the assumption that dUT1 is less than 1 second. Anything that has any relationship with astronomy, e.g. for observations or for navigation, relies on computing UT1 (i.e. the angle between the mean Sun and Earth) from time, so it would have to be updated. Changing the definition of UTC would make it completely redundant, Instead of giving up to add leap seconds to UTC, it would be much better to make a final leap of a half of minute and have TAI = UTC after the date of the big leap. Having 2 identical times with an arbitrary offset between them would just add needless complications to all time-related software, forever.
- kortex 4y ago
  > The problem is that UTC, despite its name, is not a time. Could you elaborate on what you mean? What is UTC if not a time? Like, datetimes vs time? Even if Unix time was based on TAI, you'd still need leap seconds in order to resolve the correct local time (which is based of even-minute offsets of UTC). Maybe it's easier to deal with in calculation post-hoc vs smearing on the day of, but that handful-of-accruing-seconds will always be there.
  - adrian_b 4y ago
    UT1 is an angle, i.e. the longitude of the mean Sun projected on the Earth. The mean Sun is a fictitious Sun with a motion that is averaged in comparison to the real Sun. UTC is the UT1 angle rounded to a multiple of 1/21600 of a right angle, i.e. the angle corresponding to 1 second of time for something that completes a circle in 1 day. Because of this rounding, actually a truncation, UT1 = UTC + dUT1, where dUT1 is between 0 and 1 "seconds". Even if UT1, dUT1 and UTC are expressed in "seconds", these "seconds" are not the unit of time, but like I have said, such a "second" is 1/21600 of a right angle or pi/43200 radian. Both UT1 and UTC are angles that approximate the longitude of the projection of the Sun on Earth, with various accuracies. Because the rotation of the Earth, which causes most of the apparent motion of the Sun, is almost uniform, the angle of rotation is almost proportional with the time, so the angle UTC is almost proportional with the time, i.e. with TAI. Because of the way how the "second" angle used for UT1/UTC is defined, the approximate proportionality becomes an approximate equality of TAI with UTC, but because the equality is only approximate, there is an increasing offset between them. In the ancient times, the people did not care much about time, but only about the angle of the Sun, which determined when it was light or dark, hot or cold, enabling or preventing various activities. In modern times with artificial lighting and heating and with many activities that proceed at predictable rates, time has become much more important than the angle of the Sun. In any case, in all contexts we must be aware that the angle of the Sun and the time are not the same thing, even if they are almost proportional, i.e. almost equal after a change of the measurement unit.
    - kortex 4y ago

dexwiz 4y ago

This is literally what the TIA standard is. Anything that needs precise time already uses this standard.

deleted 4y ago

[deleted]

adrian_b 4y ago

The problem is that UTC, despite its name, is not a time (it is an angle rounded to a multiple of 1/21600 right angles). Only TAI is a time. Already decades ago, some programmers have argued that internally all computers and their software should use only TAI, which is a time, so it behaves as expected, while UTC must be used exactly like the local times and the time zones, only at the interfaces with humans. If that proposal would have been adopted, there would not have been now any discussion about the leap second. The only reason for the existence of UTC is to keep dUT1, i.e. UT1 - UTC, under 1 second. If the leap second is eliminated, then dUT1 will grow over 1 second, so there are other cohorts of hardware devices and software applications that must be updated in order to no longer rely on the assumption that dUT1 is less than 1 second. Anything that has any relationship with astronomy, e.g. for observations or for navigation, relies on computing UT1 (i.e. the angle between the mean Sun and Earth) from time, so it would have to be updated. Changing the definition of UTC would make it completely redundant, Instead of giving up to add leap seconds to UTC, it would be much better to make a final leap of a half of minute and have TAI = UTC after the date of the big leap. Having 2 identical times with an arbitrary offset between them would just add needless complications to all time-related software, forever.

kortex 4y ago
> The problem is that UTC, despite its name, is not a time. Could you elaborate on what you mean? What is UTC if not a time? Like, datetimes vs time? Even if Unix time was based on TAI, you'd still need leap seconds in order to resolve the correct local time (which is based of even-minute offsets of UTC). Maybe it's easier to deal with in calculation post-hoc vs smearing on the day of, but that handful-of-accruing-seconds will always be there.
- adrian_b 4y ago
  UT1 is an angle, i.e. the longitude of the mean Sun projected on the Earth. The mean Sun is a fictitious Sun with a motion that is averaged in comparison to the real Sun. UTC is the UT1 angle rounded to a multiple of 1/21600 of a right angle, i.e. the angle corresponding to 1 second of time for something that completes a circle in 1 day. Because of this rounding, actually a truncation, UT1 = UTC + dUT1, where dUT1 is between 0 and 1 "seconds". Even if UT1, dUT1 and UTC are expressed in "seconds", these "seconds" are not the unit of time, but like I have said, such a "second" is 1/21600 of a right angle or pi/43200 radian. Both UT1 and UTC are angles that approximate the longitude of the projection of the Sun on Earth, with various accuracies. Because the rotation of the Earth, which causes most of the apparent motion of the Sun, is almost uniform, the angle of rotation is almost proportional with the time, so the angle UTC is almost proportional with the time, i.e. with TAI. Because of the way how the "second" angle used for UT1/UTC is defined, the approximate proportionality becomes an approximate equality of TAI with UTC, but because the equality is only approximate, there is an increasing offset between them. In the ancient times, the people did not care much about time, but only about the angle of the Sun, which determined when it was light or dark, hot or cold, enabling or preventing various activities. In modern times with artificial lighting and heating and with many activities that proceed at predictable rates, time has become much more important than the angle of the Sun. In any case, in all contexts we must be aware that the angle of the Sun and the time are not the same thing, even if they are almost proportional, i.e. almost equal after a change of the measurement unit.
  - kortex 4y ago