[tz] Was there a 1971-12-31 23:59:60?

Levine, Judah Dr. (Fed) judah.levine at nist.gov
Sat Nov 10 19:54:11 UTC 2018

 The current integer leap second system did not exist before 1972. There were a number of fractional-second adjustments and there were also frequency adjustments starting in the 1950s, when the length of the cesium second was defined. The final time adjustment at the start of 1972 was intended to incorporate the integral of the previous frequency steps, since the frequency of UTC was set equal to the SI second at that time. It is quite challenging to compute time intervals in the pre-1972 era.

Different timing laboratories had slightly different values for this final time step. The goal was to bring all of the real-time realizations of UTC to the same time.

Judah Levine

On: 09 November 2018 22:29, "Steve Allen" <sla at ucolick.org<mailto:sla at ucolick.org>> wrote:
On Fri 2018-11-09T22:04:35-0700 Paul Gilmartin via tz hath writ:
> Subject: [tz] Was there a 1971-12-31 23:59:60?


There was a step of 0.107758 seconds in UTC(BIH) at 1972-01-01.
This was the final sub-second step in coordinated broadcast time signals.

for the step that was applied to UTC(USNO) see
Time Service Announcement series 14 number 8 (1971-10-08)

Steve Allen                    <sla at ucolick.org<mailto:sla at ucolick.org>>              WGS-84 (GPS)
UCO/Lick Observatory--ISB 260  Natural Sciences II, Room 165  Lat  +36.99855
1156 High Street               Voice: +1 831 459 3046       &nb
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