[Python-Dev] Status on PEP-431 Timezones
tim.peters at gmail.com
Sat Jul 25 07:07:42 CEST 2015
> Sure. But, honestly, who cares? Riyadh Solar Time was so
> off-the-wall that even the Saudis gave up on it 25 years ago (after a
> miserable 3-year experiment with it). "Practicality beats purity".
Heh. It's even sillier than that - the Saudis never used "Riyadh
Solar Time", and it's been removed from release 2015e of the tz
Release 2015e - 2015-06-13 10:56:02 -0700
The files solar87, solar88, and solar89 are no longer distributed.
They were a negative experiment - that is, a demonstration that
tz data can represent solar time only with some difficulty and error.
Their presence in the distribution caused confusion, as Riyadh
civil time was generally not solar time in those years.
Looking back, Paul Eggert explained more in 2013, but it took this
long for the patch to land:
> did Saudi Arabia really use this as clock time?
Not as far as I know, for civil time. There was some use
for religious purposes but it didn't use the approximation
in those files.
These files probably cause more confusion than they're worth,
so I'll propose a couple of patches to remove them, in two followup
emails. I haven't pushed these patches to the experimental
The position of the sun is vital to establishing prayer times in
Islam, but that's got little to do with civil time in Islamic
countries. And Olson didn't take his "Riyadh Solar Time" rules from
the Saudis, he made up the times himself: "Times were computed using
formulas in the U.S. Naval Observatory's Almanac for Computers
1987". The formulas only produced approximations, and then
rounded to 5-second boundaries because the tz data format didn't have
So, as a motivating example, it's hard to get less compelling: Riyadh
Solar is a wholly artificial "time zone" made up by a time zone wonk
to demonstrate some limitations of the tz database he maintained.
Although I expect he could have done so just as effectively by writing
a brief note about it ;-)
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