Hello all,

I have recently received some new information about timezone history of Bonin Islands, Japan as detailed in the attached message.

Because their last time change to return to Japanese time when they return to Japanese rule was right before 1970, it mean per the current tz database rule, the information doesn't warrant creation of a new timezone for Bonin Islands itself and is thus as an anecdotal note for interest purpose only.

However, in the attached link, it described some special timekeeping phenomenon regarding Marcus island, another remote island currently owned by Japanese in the same administrative unit as Bonin Islands.

Many reports claim that the American coastal guard on the American quarter of the island use its own coastal guard time, and most sources describe the time as UTC+11, being two hours faster than JST used by some Japanese personnel on the island. Some sites describe it as same as Wake Island/Guam time although it would be incorrect to be same as Guam.

And then in a few Japanese governmental report from 1980s (from National Institute of Information and Communications Technology) regarding the construction of VLBI facility on the Marcus Island, it claimed that there're three time standard being used on the island at the time which include not just JST (UTC+9) or [US]CG time (UTC+11) but also a JMSDF time (UTC+10) (Japan Maritime Self-Defense Force). Unfortunately there are no other sources that mentioned such time and there are also no information on things like how the tine was used.

---------- Forwarded message ---------
From: Wakaba
Date: 2019-1-28 Mon 13:48
Subject: Re: Question related to the page 昭和のサマータイム on suikawiki
To: Phake Nick

>> Hello, I see that there're a lot of information about DST at the time in Japan on Suikawiki, but a special area that's not mentioned in the page os Ogasawara 小笠原諸島 (Bonin Islands) which seems to have its own different history of governance. Do you know where can information related to timezone of the islands can be found?

> Unfortunately we have no reliable source on time in US-controlled Ogasawara Islands at the moment.

It turns out that National Diet Library of Japan has several reports
by Japanese Government officers that describe the time used in islands
when they visited there. According to them (and other sources such as
newspapers), standard time UTC + 10 (JST + 1) and DST UTC + 11 (JST +
2) was used until its return to Japan at 1968-06-26 00:00 JST.

The exact periods of DST are still unknown. I guessed Guam, Mariana,
and Bonin and Marcus districts might have synchronized their DST
periods, but reports imply they had their own decisions, i.e. there
were three or more different time zones.

Details:

https://wiki.suikawiki.org/n/%E5%B0%8F%E7%AC%A0%E5%8E%9F%E8%AB%B8%E5%B3%B6%E3%81%AE%E6%A8%99%E6%BA%96%E6%99%82