[tz] Japanese Summer time fallback transition in autumn 2020?

Paul Ganssle paul at ganssle.io
Tue Sep 18 20:43:02 UTC 2018

To clarify, I think the official name of the hours is less important
than *when* the transition occurred.

The law says that the last day of DST had 25 hours instead of 24. The
question is whether in practice what happened was that starting 0:00 on
Saturday, did people wait 25 hours (until 01:00 on Sunday) and THEN set
their clocks back 1 hour, or did they wait 24 hours (until 00:00 on
Sunday), and then set the clock back to 23:00?



On 9/18/18 2:00 AM, horonet at ml.nict.go.jp wrote:
> Dear Sirs,
> Thank you for your email dated September 12, 2018.
> We really appreciate your interest and comment.
> Unfortunately, we have no information on the official name of
> additional hours past the 12th o'clock midnight on the last DST day of
> Japan.
> If you ask NAOJ, you may be able to get more information.
> NAOJ and NAOJ Ephemeris Computation Office's Websites:
> https://www.nao.ac.jp/en/
> https://eco.mtk.nao.ac.jp/koyomi/index.html.en
> Thank you for another question about DST in 2020.
> The government is considering future DST in Japan, but nothing has
> been decided yet.
> Thank you for your understanding.
> We wish good luck to you.
> Sincerely,
> Japan Standard Time Group
> Space-Time standards Laboratory
> Applied Electromagnetic Research Institute
> National Institute of Information and Communications Technology
> http://www.nict.go.jp/
> On 2018/09/12 2:00, Paul Eggert wrote:
>> One other thing. The Japanese government is considering adopting
>> daylight saving time for the 2020 Tokyo Olympics. Will this issue about
>> 25-hour (or 26-hour) days come up in 2020? For example, could there be a
>> 26-hour day in September 2020 with times ranging from 00:00 to 26:00? If
>> so, a *lot* of computers will have to be reprogrammed, as no software
>> I'm aware of supports timestamps like that now.

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