Vietnam follows UTC+7, which is 7 hours ahead of UTC, ICT is used all year round as Vietnam does not observe daylight saving time.
ISO 8601 under in 1998 and then created its own standard TCVN 6398-1:1998. 
History [ edit ]
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 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 GMT+8, skipping 60 minutes at 23:00 31 December 1942. The
Japan occupied Vichy French Indochina fully. Indochinese regions thereafter followed Tokyo time zone (GMT+9), 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 GMT+7 as official time zone on 2 September 1945. Whilst, the then under-attacked regions of Vietnam, Laos and Cambodia adopted GMT+8 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 GMT+7 from 00:00 1 July 1955. South Vietnam time zone was changed to GMT+8 from 23:00 1 January 01 1960, passing 60 minutes.
North Vietnam confirmed official UTC+7 from 1 January 1968.
Fall of Saigon in April–May 1975, reunified Vietnam then observes UTC+7 with Saigon (and other southern parts) delaying 60 minutes on 13 June 1975.
Time in French Indochina [ edit ]
Time in North Vietnam [ edit ]
Time in South Vietnam [ edit ]
Time in Reunified Vietnam [ edit ]
Period in use
Time offset from GMT
13 June 1975 - now
Standard Zone Time
See also [ edit ]
References [ edit ]
Bibliography [ edit ]
Trần Tiến Bình (2005),
Lịch Việt Nam thế kỷ XX-XXI (1901-2100), Nhà xuất bản Văn hoá Thông tin, Hanoi.