[LEAPSECS] Civil timekeeping before 1 January 1972

[G Ashton]

Brooks Harris wrote on Saturday, March 7, 2015 11:50 :
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"The challenge I'm trying to solve is to provide a deterministic timekeeping
and labeling scheme for date and time *after* 1972-01-01T00:00:00Z (UTC) =
1972-01-01T00:00:10 (TAI). This is essentially the purpose of "civil time"
timekeeping as is typically intended....The timescale before 1972 is an
abstract proleptic Gregorian calendar scale for purposes of calculation
convenience. On this scale, like NTP, PTP, and POSIX, any date-time before
1972-01-01T00:00:00Z (UTC) is considered either inaccurate or invalid."

Civil timekeeping is concerned with many things, including determining when
one date ends and another begins. Thus civil timekeeping is inextricably
linked to civil calendars. Although the time of day of past events become
less and less important as the decades pass, the date of those events remain
important. Since some computer applications routinely attempt, in their
clumsy way, to account for timezones, timekeeping is potentially important
for the computer representation of timestamps, even when the humans using
the computer are only interested in the date. Of course, dates long before
1972 are of interest in civil matters; dates of birth immediately come to
mind. So when Brooks Harris presents his API to his stakeholders, I think a
more thorough explanation of why date-time expressions before 1972 will be "
considered either inaccurate or invalid" will be needed.

Gerard Ashton