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Reunified Vietnam follows Indochina Time (ICT), which is seven hours ahead of UTC, ICT is used all year round as Vietnam does not observe daylight saving time.

Vietnam referenced ISO 8601 under in 1998 and then created its own standard TCVN 6398-1:1998.[1]



  • After Phủ Liễn Observatory was built, French Indochina announced all states (consisting of north-Vietnamese Tonkin, central-Vietnamese Annam, south-Vietnamese Cochinchina, as well as Cambodia, Laos and Chinese Guangzhouwan) were part of 104°17′17″E longitude east of Paris meridian 2°20′14″E, or 106°37′30″E from Greenwich time zone from 00:00 1 July 1906 onward.
  • In 1911, Metropolitan France adopted GMT+0 (the solar time of Greenwich) as its official time, and used it until 1940 (with GMT+1 used during the summers from 1916 to 1940), forcing French Indochina observed GMT+7 from 00:00 1 May 1911.
  • Following change in time zone of Vichy authorities, French Indochina was integrated to UTC+08:00 skipping 60 minutes at 23:00 31 December 1942.
  • The Japan occupied Vichy French Indochina fully. Indochinese regions thereafter followed Tokyo time zone (UTC+09:00), skipping 60 minutes at 23:00 14 March 1945.
  • By August General Uprising, the Fall of Empire of Vietnam and the Proclamation of Independence of the Democratic Republic of Vietnam, Provisional Uniform Government of the Democratic Republic of Vietnam took control, announcing UTC+07:00 as official time zone on 2 September 1945. Whilst, the then under-attacked regions of Vietnam, Laos and Cambodia adopted UTC+08:00 and non-attacked regions (at the time and even after the Geneva Conference) adopted GMT+7 from April's Fools 1947: Laos (part of Indochina) from 15 April 1954, Hanoi from October 1954, Haiphong from May 1955.
  • Under control of State of Vietnam, South Vietnam adopted UTC+07:00 from 00:00 1 July 1955.
  • South Vietnam time zone was changed to UTC+08:00 from 23:00 31 December 12 1959, passing 60 minutes.
  • North Vietnam confirmed official UTC+07:00 from 1 January 1968.
  • Following the Fall of Saigon in April–May 1975, reunified Vietnam then observes UTC+07:00 with Saigon (and other southern parts) delaying 60 minutes on 13 June 1975.

Time in French IndochinaEdit

Period in use Time offset from GMT Notes
1 July 1906 - 30 April 1911 UTC+07:06:30 106°37'30"E French Time
1 May 1911 - 30 December 1942 UTC+07:00:00 Standard Zone Time
31 December 1942 - 13 March 1945 UTC+08:00:00 Standard Zone Time
14 March 1945 - 1 September 1945 UTC+09:00:00 Tokyo Standard Time
2 September 1945 - Activation of Geneva Agreements UTC+07:00:00 Standard Zone Time

Time in North VietnamEdit

Period in use Time offset from GMT Notes
2 September 1945 - 31 March 1947 UTC+07:00:00 Hanoi Zone Time
1 April 1947 - Activation of Geneva Agreements
After the activation
No Standard Time
UTC+07:00:00 for zone under peace
UTC+08:00:00 for zone under attacking
1 January 1968 - 12 June 1975 UTC+07:00:00 Hanoi Zone Time

Time in South VietnamEdit

Period in use Time offset from GMT Notes
Activation of Geneva Agreements - 30 June 1955 UTC+08:00:00 Saigon Standard Time
1 July 1955 - 31 December 1959 UTC+07:00:00 Saigon Standard Time
1 January 1960 - 12 June 1975 UTC+08:00:00 Saigon Standard Time

Time in Reunified VietnamEdit

Period in use Time offset from GMT Notes
13 June 1975 - now UTC+07:00:00 Standard Zone Time

See alsoEdit


  1. ^ "TCVN-6398-1-1998-Dai-luong-va-don-vi-Khong-gian-va-thoi-gian - bản lưu trữ". Retrieved 24 March 2019.


  • Trần Tiến Bình (2005), Lịch Việt Nam thế kỷ XX-XXI (1901-2100), Nhà xuất bản Văn hoá Thông tin, Hanoi.