TAI zone?

Guy Harris guy at alum.mit.edu
Thu Jun 30 04:39:03 UTC 2011

On Jun 29, 2011, at 10:16 AM, Olson, Arthur David (NIH/NCI) [E] wrote:

> Is there any reason why a TAI "time zone" ("TZ=TAI; export TZ") is not
> present for those that want to ignore leap seconds?

What day is it right now? :-)

>From what I can find, TAI is defined as "seconds since the TAI epoch", which, if this page


is correct, is "1958 January 1 d 0 h 0 min 0 s"; if so, presumably that's "1958 January 1 d 0 h 0 min 0 s GMT".

I suspect that means that the answer to "what day is it right now" could differ between the UTC and TAI zones near the insertion of a leap second.  Then again, it could differ between different locations on the earth....

(And, yes, that would appear to mean that, if you were to take the phrase "seconds since the Epoch" literally, if a TAI value is represented as DDDDDDD/HH/MM/SS, then the corresponding time_t value is

	DDDDDDD*86400 + HH*3600 + MM*60 + SS - {number of seconds from 1958-01-01 00:00:00 GMT to 1970-01-01 00:00:00 UTC}

but, of course, POSIX doesn't take that phrase literally....)

However, as per what Robert Elz said, time_t is defined to be adjusted for leap seconds in ways that make it a pain to convert it to TAI....

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