On Thu 2023-03-09T13:30:52-0800 Paul Eggert via tz hath writ:
Leap Second Table: A record of a series of consecutive leap seconds.
Leap Second Table Expiration: The cutoff time for a leap second table, such that the table does not record the presence or absence of leap seconds on or after the cutoff. For example, a leap second table published in January, which predicts the presence or absence of a leap second at June's end, might expire in mid-December because when the table is published it is not known whether a leap second will occur at December's end.
Be aware that this six month expiration cycle is a leftover from the Soviet demands at the inception of leap-seconds and is not explicit in any regulatory document. It is tradition, albeit long established. -- Steve Allen <sla@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 Lng -122.06015 Santa Cruz, CA 95064 https://www.ucolick.org/~sla/ Hgt +250 m