[Datetime-SIG] Computing .dst() as a timedelta
alexander.belopolsky at gmail.com
Wed Sep 23 04:45:19 CEST 2015
On Tue, Sep 22, 2015 at 10:27 PM, Chris Angelico <rosuav at gmail.com> wrote:
> [ Alexander Belopolsky] but I cannot tell you "mean" of what it is or
> whether BBC's
> > fifth beep comes on a UTC or GMT second.
> Yes, it's because GMT is based on the average solar noon. If you have
> an actual sundial, you can observe actual solar noon, but to convert
> that to civil time, you need a table of translations that takes
> seasonal variation into account. In theory, Greenwich Time would show
> noon when the sun is directly overhead, but that would mean that
> successive days vary in length; Greenwich Mean Time averages it all
> out so you get a consistent 86400-second day.
> UTC is defined by the coordination of a bunch of clocks around the
> world. There are a few different forms, most of which never go more
> than one second away from each other. GMT is usually defined as being
> equal to one or other of them, but which one is not entirely
> standardized, so if you need subsecond accuracy, don't use GMT at all.
> For scheduling events, though, GMT == UTC == TIA == Unix time.
Thanks for the lecture, but I still don't know what BBC broadcasts. :-)
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