3 ms·

> At the beginning, the leap second duration between POSIX and TAI was smeared over years from one leap second to the other. So the difference between both time

> At the beginning, the leap second duration between POSIX and TAI was smeared over years from one leap second to the other. So the difference between both timestamps would change continually other these periods! Do you have any reference to a system that was implemented this way? I have never heard of such a thing and I don't see how it could be implemented. The insertion of leap seconds is unpredictable and occurs when the International Earth Rotation and Reference Systems Service determines that the difference between UTC and UT1 are approaching 0.9 seconds. Leap seconds are generally only decided six months or so before they occur. So you don't know at the beginning of the year how many leap seconds the year will have. So it doesn't seem possible to smear over a year.

demurgos 7y ago
I remember reading it from Wikipedia some times ago. I looked it up again and I was wrong: this was not applied for POSIX but UTC itself. The arrival of international networks seems to actually be the reason why they stopped smearing it continually and switched to a linear version with discontinuities. [0] > UTC is a discontinuous time scale. From its beginning in 1961 through December 1971 the adjustments were made regularly in fractional leap seconds so that UTC approximated UT2. Afterwards these adjustments were made only in whole seconds to approximate UT1. This was a compromise arrangement in order to enable a publicly broadcast time scale; the post-1971 more linear transformation of the BIH's atomic time meant that the time scale would be more stable and easier to synchronize internationally. Wikipedia sources it to a book [1]. [0]: https://en.wikipedia.org/wiki/International_Atomic_Time#Relation_to_UTC https://en.wikipedia.org/wiki/International_Atomic_Time#Rela... [1]: McCarthy, Dennis D.; Seidelmann, Kenneth P. (2009). Time: From Earth Rotation to Atomic Physics. Weinheim: Wiley-VCH Verlag GmbH & Co. KGaA. ISBN 978-3-527-40780-4.

demurgos 7y ago

I remember reading it from Wikipedia some times ago. I looked it up again and I was wrong: this was not applied for POSIX but UTC itself. The arrival of international networks seems to actually be the reason why they stopped smearing it continually and switched to a linear version with discontinuities. [0] > UTC is a discontinuous time scale. From its beginning in 1961 through December 1971 the adjustments were made regularly in fractional leap seconds so that UTC approximated UT2. Afterwards these adjustments were made only in whole seconds to approximate UT1. This was a compromise arrangement in order to enable a publicly broadcast time scale; the post-1971 more linear transformation of the BIH's atomic time meant that the time scale would be more stable and easier to synchronize internationally. Wikipedia sources it to a book [1]. [0]: https://en.wikipedia.org/wiki/International_Atomic_Time#Relation_to_UTC https://en.wikipedia.org/wiki/International_Atomic_Time#Rela... [1]: McCarthy, Dennis D.; Seidelmann, Kenneth P. (2009). Time: From Earth Rotation to Atomic Physics. Weinheim: Wiley-VCH Verlag GmbH & Co. KGaA. ISBN 978-3-527-40780-4.