[LEAPSECS] temporal confusion

Steve Allen sla at ucolick.org
Tue Mar 27 00:41:58 EDT 2012

A close reading of IEEE 1588-2002 and IEEE 1588-2008 (the PTP
standard) seems to indicate some confusion.

The normative text of both 2002 and 2008 seems pretty clear that the
PTP time scale is supposed to match the number of seconds of TAI
elapsed since 1970-01-01T00:00:00 in proleptic TAI, the BIH atomic
time scale which later became TAI.

Appendix B of the 2002 standard indicates unclearly that the PTP time
scale is TAI - 10 s (equivalent to the LORAN-C time scale, the "right"
zoneinfo time scale, and the canonical IBM z/OS time scale).

The 2008 standard seems to correct the confusion largely by omitting
most of the self-contradictory content of the original Appendix B.
Nevertheless, there are several references to PTP which repeat the
content of the original and say that PTP is TAI - 10 s.

Is there any clear explanation of what happened?

Steve Allen <sla at ucolick.org> WGS-84 (GPS)
UCO/Lick Observatory--ISB Natural Sciences II, Room 165 Lat +36.99855
1156 High Street Voice: +1 831 459 3046 Lng -122.06015
Santa Cruz, CA 95064 http://www.ucolick.org/~sla/ Hgt +250 m

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