[LEAPSECS] Footnote about CCITT and UTC
dot at dotat.at
Mon Dec 15 07:01:11 EST 2008
On Sun, 14 Dec 2008, Zefram wrote:
> NOTE These expressions apply to both UTC and non-UTC based time
> scales for time of day.
> This seems to be the crucial bit that you missed. It's explicit about
> allowing time scales other than UTC, and doesn't restrict the choice
> of time scale at all. UT1, with strict 86400-second days, is obviously
> permitted, and I suggest that vague UT per se is also a valid time scale.
Ah, yes, thanks for pointing that out, and also
> *local time*
> locally applicable time of day such as standard time of day,
> or a non-UTC based time of day
> You're permitted to represent, for example, the mean-solar-time-based
> British legal time in ISO 8601.
> Unfortunately ISO 8601 does not supply any way to designate UT1 or any
> other flavour of UT except UTC. Thus, strictly speaking, there is no
> way to designate any local time that is based on UT1 rather than UTC.
So non-UTC time has only minimal support by the standard.
> It seems to me that the standard would be rather more useful if "standard
> time" were defined more according to its original meaning: a local time
> scale defined by an offset from UT, rather than specifically from UTC.
> The timezone designation material should correspondingly refer to UT
> rather than UTC, and the "Z" should probably follow by designating UT.
> All of these would be explicitly vague as to which flavour of UT is
> being referred to.
Yes, I think this kind of vagueness makes sense in a lot of situations
(with appropriate caveats for applications that require subsecond
precision and agreement between multiple systems). It would work for POSIX
f.anthony.n.finch <dot at dotat.at> http://dotat.at/
FORTIES CROMARTY FORTH: SOUTHERLY 5 TO 7, PERHAPS GALE 8 LATER. ROUGH OR VERY
ROUGH, BECOMING MODERATE OR ROUGH. FAIR THEN RAIN. MODERATE OR POOR.
More information about the LEAPSECS