Asia/Ho_Chi_Minh

Time zone identifier: Asia/Ho_Chi_Minh

Current civil offset: +07:00 (+07)

Current DST state: Observing Standard Time

First standard time adoption: Adopted on 1906-06-30

Local Mean Time (LMT): +07:06:30 based on geographic meridian

Total recorded transitions: 9 transitions across 4 distinct offsets

Associated countries: VN

Aliases (Link targets): Asia/Saigon

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Historical Offset Step Chart (1880 to Present)

+6:00 +7:00 +8:00 +9:00 +10:00 1880 1900 1920 1940 1960 1980 2000 2020

Text summary: Asia/Ho_Chi_Minh shifted between 4 distinct offsets from 1906-06-30 through the modern era.

Complete Transition History (9 Transitions)

UTC Instant Local Wall Time Shift Abbreviation DST Effect
1906-06-30T16:53:30Z 1906-07-01 00:00:00 +07:06:30 → +07:06:30 PLMT No offset-only
1911-04-30T16:53:30Z 1911-04-30 23:53:30 +07:06:30 → +07:00 +07 No overlap
1942-12-31T16:00:00Z 1943-01-01 00:00:00 +07:00 → +08:00 +08 No gap
1945-03-14T15:00:00Z 1945-03-15 00:00:00 +08:00 → +09:00 +09 No gap
1945-09-01T15:00:00Z 1945-09-01 22:00:00 +09:00 → +07:00 +07 No overlap
1947-03-31T17:00:00Z 1947-04-01 01:00:00 +07:00 → +08:00 +08 No gap
1955-06-30T17:00:00Z 1955-07-01 00:00:00 +08:00 → +07:00 +07 No overlap
1959-12-31T16:00:00Z 1960-01-01 00:00:00 +07:00 → +08:00 +08 No gap
1975-06-12T16:00:00Z 1975-06-12 23:00:00 +08:00 → +07:00 +07 No overlap

Notes from the Maintainers

Source: asia (Lines 4154 to 4229)
Vietnam (southern)

From Paul Eggert (2014-10-04):
Milne gives 7:16:56 for the meridian of Saigon in 1899, as being
used in Lower Laos, Cambodia, and Annam.  But this is quite a ways
from Saigon's location.  For now, ignore this and stick with Shanks
and Pottenger for LMT before 1906.

From Arthur David Olson (2008-03-18):
The English-language name of Vietnam's most populous city is "Ho Chi Minh
City"; use Ho_Chi_Minh below to avoid a name of more than 14 characters.

From Paul Eggert (2024-01-14) after a 2014 heads-up from Trần Ngọc Quân
and a 2024-01-14 heads-up from Đoàn Trần Công Danh:
Trần Tiến Bình's authoritative book "Lịch Việt Nam: thế kỷ XX-XXI (1901-2100)"
(Nhà xuất bản Văn Hoá - Thông Tin, Hanoi, 2005), pp 49-50,
is quoted verbatim in:
http://www.thoigian.com.vn/?mPage=P80D01
is translated by Brian Inglis in:
https://mm.icann.org/pipermail/tz/2014-October/021654.html
and is the basis for the information below.

The 1906 transition was effective July 1 and standardized Indochina to
Phù Liễn Observatory, legally 104° 17' 17" east of Paris.
It's unclear whether this meant legal Paris Mean Time (00:09:21) or
the Paris Meridian; for now guess the former and round the exact
07:06:30.1333... to 07:06:30.13 as the legal spec used 66 2/3 ms precision.
which is used below even though the modern-day Phù Liễn Observatory
is closer to 07:06:31.  Abbreviate Phù Liễn Mean Time as PLMT.

The following transitions occurred in Indochina in general (before 1954)
and in South Vietnam in particular (after 1954):
To 07:00 on 1911-05-01.
To 08:00 on 1942-12-31 at 23:00.
To 09:00 on 1945-03-14 at 23:00.
To 07:00 on 1945-09-02 in Vietnam.
To 08:00 on 1947-04-01 in French-controlled Indochina.
To 07:00 on 1955-07-01 in South Vietnam.
To 08:00 on 1959-12-31 at 23:00 in South Vietnam.
To 07:00 on 1975-06-13 in South Vietnam.

Trần cites the following sources; it's unclear which supplied the info above.

Hoàng Xuân Hãn: "Lịch và lịch Việt Nam". Tập san Khoa học Xã hội,
No. 9, Paris, February 1982.

Lê Thành Lân: "Lịch và niên biểu lịch sử hai mươi thế kỷ (0001-2010)",
NXB Thống kê, Hanoi, 2000.

Lê Thành Lân: "Lịch hai thế kỷ (1802-2010) và các lịch vĩnh cửu",
NXB Thuận Hoá, Huế, 1995.

Here is the decision for the September 1945 transition:
Võ Nguyên Giáp, Việt Nam Dân Quốc Công Báo, No. 1 (1945-09-29), page 13
http://baochi.nlv.gov.vn/baochi/cgi-bin/baochi?a=d&d=JwvzO19450929.2.5&dliv=none
It says that on 1945-09-01 at 24:00, Vietnam moved back two hours, to +07.
It also mentions a 1945-03-29 decree (by a Japanese Governor-General)
to set the time zone to +09, but does not say whether that decree
merely legalized an earlier change to +09.

July 1955 transition:
Ngô Đình Diệm, Công Báo Việt Nam, No. 92 (1955-07-02), page 1780-1781
Ordinance (Dụ) No. 46 (1955-06-25)
http://ddsnext.crl.edu/titles/32341#?c=0&m=29&s=0&cv=4&r=0&xywh=-89%2C342%2C1724%2C1216
It says that on 1955-07-01 at 01:00, South Vietnam moved back 1 hour (to +07).

December 1959 transition:
Ngô Đình Diệm, Công Báo Việt Nam Cộng Hòa, 1960 part 1 (1960-01-02), page 62
Decree (Sắc lệnh) No. 362-TTP (1959-12-30)
http://ddsnext.crl.edu/titles/32341#?c=0&m=138&s=0&cv=793&r=0&xywh=-54%2C1504%2C1705%2C1202
It says that on 1959-12-31 at 23:00, South Vietnam moved forward 1 hour (to +08).


Zone	NAME		STDOFF	RULES	FORMAT	[UNTIL]
STDOFF	7:06:30.13

Attributed Statements:

Paul Eggert (2014-10-04):

Milne gives 7:16:56 for the meridian of Saigon in 1899, as being used in Lower Laos, Cambodia, and Annam. But this is quite a ways from Saigon's location. For now, ignore this and stick with Shanks and Pottenger for LMT before 1906.

Arthur David Olson (2008-03-18):

The English-language name of Vietnam's most populous city is "Ho Chi Minh City"; use Ho_Chi_Minh below to avoid a name of more than 14 characters. From Paul Eggert (2024-01-14) after a 2014 heads-up from Trần Ngọc Quân and a 2024-01-14 heads-up from Đoàn Trần Công Danh: Trần Tiến Bình's authoritative book "Lịch Việt Nam: thế kỷ XX-XXI (1901-2100)" (Nhà xuất bản Văn Hoá - Thông Tin, Hanoi, 2005), pp 49-50, is quoted verbatim in: http://www.thoigian.com.vn/?mPage=P80D01 is translated by Brian Inglis in: https://mm.icann.org/pipermail/tz/2014-October/021654.html and is the basis for the information below. The 1906 transition was effective July 1 and standardized Indochina to Phù Liễn Observatory, legally 104° 17' 17" east of Paris. It's unclear whether this meant legal Paris Mean Time (00:09:21) or the Paris Meridian; for now guess the former and round the exact 07:06:30.1333... to 07:06:30.13 as the legal spec used 66 2/3 ms precision. which is used below even though the modern-day Phù Liễn Observatory is closer to 07:06:31. Abbreviate Phù Liễn Mean Time as PLMT. The following transitions occurred in Indochina in general (before 1954) and in South Vietnam in particular (after 1954): To 07:00 on 1911-05-01. To 08:00 on 1942-12-31 at 23:00. To 09:00 on 1945-03-14 at 23:00. To 07:00 on 1945-09-02 in Vietnam. To 08:00 on 1947-04-01 in French-controlled Indochina. To 07:00 on 1955-07-01 in South Vietnam. To 08:00 on 1959-12-31 at 23:00 in South Vietnam. To 07:00 on 1975-06-13 in South Vietnam. Trần cites the following sources; it's unclear which supplied the info above. Hoàng Xuân Hãn: "Lịch và lịch Việt Nam". Tập san Khoa học Xã hội, No. 9, Paris, February 1982. Lê Thành Lân: "Lịch và niên biểu lịch sử hai mươi thế kỷ (0001-2010)", NXB Thống kê, Hanoi, 2000. Lê Thành Lân: "Lịch hai thế kỷ (1802-2010) và các lịch vĩnh cửu", NXB Thuận Hoá, Huế, 1995. Here is the decision for the September 1945 transition: Võ Nguyên Giáp, Việt Nam Dân Quốc Công Báo, No. 1 (1945-09-29), page 13 http://baochi.nlv.gov.vn/baochi/cgi-bin/baochi?a=d&d=JwvzO19450929.2.5&dliv=none It says that on 1945-09-01 at 24:00, Vietnam moved back two hours, to +07. It also mentions a 1945-03-29 decree (by a Japanese Governor-General) to set the time zone to +09, but does not say whether that decree merely legalized an earlier change to +09. July 1955 transition: Ngô Đình Diệm, Công Báo Việt Nam, No. 92 (1955-07-02), page 1780-1781 Ordinance (Dụ) No. 46 (1955-06-25) http://ddsnext.crl.edu/titles/32341#?c=0&m=29&s=0&cv=4&r=0&xywh=-89%2C342%2C1724%2C1216 It says that on 1955-07-01 at 01:00, South Vietnam moved back 1 hour (to +07). December 1959 transition: Ngô Đình Diệm, Công Báo Việt Nam Cộng Hòa, 1960 part 1 (1960-01-02), page 62 Decree (Sắc lệnh) No. 362-TTP (1959-12-30) http://ddsnext.crl.edu/titles/32341#?c=0&m=138&s=0&cv=793&r=0&xywh=-54%2C1504%2C1705%2C1202 It says that on 1959-12-31 at 23:00, South Vietnam moved forward 1 hour (to +08). Zone NAME STDOFF RULES FORMAT [UNTIL] STDOFF 7:06:30.13

Years on Record

Methodology Note: The 1970 Rule

tzdb guarantees accuracy for timestamps from 1970 onwards. Transitions prior to 1970 represent best-effort historical reconstructions.