Does NTP work correctly with enabled Tokyo Daylight Saving Time?
I have heard that there is a possibility to start summer time, Daylight Saving Time, at Tokyo within years, around Tokyo Olympic. So I investigated if ntpd would work under daylight saving time at Tokyo.
The ntpd module of almost Linux distributions are referring /etc/localtime, which is a timezone file itself or symbolic link of any timezone files.
root@server:~# file /etc/localtime /etc/localtime: timezone data, version 2, 3 gmt time flags, 3 std time flags, no leap seconds, 9 transition times, 3 abbreviation chars root@server:~# cat /etc/issue Debian GNU/Linux 8 \n \l #
And all zone files are saved at /usr/share/zoneinfo.
root@server:/usr/share/zoneinfo# ls Africa Atlantic Canada EST5EDT Factory GMT-0 Iceland Japan MST7MDT PRC ROC UCT WET posix America Australia Chile Egypt GB GMT0 Indian Kwajalein Mexico PST8PDT ROK US Zulu posixrules Antarctica Brazil Cuba Eire GB-Eire Greenwich Iran Libya NZ Pacific Singapore UTC iso3166.tab right Arctic CET EET Etc GMT HST Israel MET NZ-CHAT Poland SystemV Universal leap-seconds.list zone.tab Asia CST6CDT EST Europe GMT+0 Hongkong Jamaica MST Navajo Portugal Turkey W-SU localtime root@server:/usr/share/zoneinfo#
Some of zone has 2 files, for example, EST and EST5EDT. One is DST timezone file, and the other is not DST timezone file. Those of them are binary file and I'm not sure how to read it. But, Tokyo zone file is only one.
root@server:/usr/share/zoneinfo# ls Asia/
Aden Baghdad Calcutta Dhaka Hong_Kong Kamchatka Kuala_Lumpur Muscat Pyongyang Seoul Tel_Aviv Urumqi
Almaty Bahrain Chita Dili Hovd Karachi Kuching Nicosia Qatar Shanghai Thimbu Ust-Nera
Amman Baku Choibalsan Dubai Irkutsk Kashgar Kuwait Novokuznetsk Qyzylorda Singapore Thimphu Vientiane
Anadyr Bangkok Chongqing Dushanbe Istanbul Kathmandu Macao Novosibirsk Rangoon Srednekolymsk Tokyo Vladivostok
Aqtau Barnaul Chungking Gaza Jakarta Katmandu Macau Omsk Riyadh Taipei Tomsk Yakutsk
Aqtobe Beirut Colombo Harbin Jayapura Khandyga Magadan Oral Saigon Tashkent Ujung_Pandang Yangon
Ashgabat Bishkek Dacca Hebron Jerusalem Kolkata Makassar Phnom_Penh Sakhalin Tbilisi Ulaanbaatar Yekaterinburg
Ashkhabad Brunei Damascus Ho_Chi_Minh Kabul Krasnoyarsk Manila Pontianak Samarkand Tehran Ulan_Bator Yerevan
root@server:/usr/share/zoneinfo#
So, at the current release, there is no way to enable DST in Tokyo on the ntpd, I believe.