[tz] JavaScript IANA date/time library, now with support for leap seconds, TAI, TDT

John Sauter John_Sauter at systemeyescomputerstore.com
Mon Apr 26 21:57:57 UTC 2021

On Mon, 2021-04-26 at 15:06 -0600, Paul Gilmartin via tz wrote:
> On 2021-04-26, at 13:15:22, Kerry Shetline via tz wrote:
> >    ...
> > > * There is a fixed, defined relationship between POSIX time and
> > > future
> > >   calendar dates and times, but that isn't true for TAI.
> > 
> > POSIX time is really just UTC without the leap seconds, isn’t it?
POSIX says, in section 4.16, that time is counted from 1970.  UTC
didn't exist in 1970, so PTP (as specified in SMPTE ST-2059-2)
specifies 1972 as the base date, with an offset of 63,072,010.

If you try to convert the PTP integer into civil time for display
purposes, you need to deal with the values 15,638,408 and 47,174,409. 
These correspond to the two leap seconds between 1970 and 1972 in Tony
Finch's table: June 30, 1970 and June 30, 1971 at 23:59:60 UTC.
    John Sauter (John_Sauter at systemeyescomputerstore.com)
get my PGP public key with gpg --locate-external-keys
John_Sauter at systemeyescomputerstore.com

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