Asia/Phnom_Penh

Time zone identifier: Asia/Phnom_Penh

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): +06:59:40 based on geographic meridian

Total recorded transitions: 5 transitions across 5 distinct offsets

Associated countries: KH

Historical Offset Step Chart (1880 to Present)

Text summary: Asia/Phnom_Penh shifted between 5 distinct offsets from 1906-06-30 through the modern era.

Complete Transition History (5 Transitions)

UTC Instant	Local Wall Time	Shift	Abbreviation	DST	Effect
`1906-06-30T17:00:20Z`	`1906-07-01 00:06:50`	+06:59:40 → +07:06:30	`PLMT`	No	gap
`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

Notes from the Maintainers

Source: backzone (Lines 1086 to 1118)

India
From Tim Parenti (2024-07-01), per Paul Eggert (2014-08-11), after a
heads-up from Stephen Colebourne:
According to a Portuguese decree (1911-05-24), Portuguese India switched to
UT +05 on 1912-01-01 (see Europe/Lisbon).
Zone	Asia/Panaji	[not enough info to complete]

Cambodia

From an adoptive daughter of the late Cambodian ruler Prince Sihanouk,
via Alois Treindl (2019-08-08):

King Sihanouk said that, during the Japanese occupation, starting with
what historians refer to as "le coup de force du 9 mars 1945", Cambodia,
like the entire French Indochina, used Tokyo time zone. After Japan
surrendered, 2 September 1945, Cambodia fell under French rule again and
adopted Hanoi time zone again.

However, on 7 January 1946, Sihanouk and Tioulong managed to obtain a
status of "internal autonomy" from the government of Charles de Gaulle.
Although many fields remained under the administration of the French
(customs, taxes, justice, defence, foreign affairs, etc.), the Cambodian
administration was responsible for religious matters and traditional
celebrations, which included our calendar and time.  The time zone was GMT
+ 7 and _no_ DST was applied.

After Sihanouk and Tioulong achieved full independence, on 9 November 1953,
GMT + 7 was maintained.

From Paul Eggert (2019-08-26):
See Asia/Ho_Chi_Minh for the source for most of rest of this data.

Attributed Statements:

Paul Eggert (2019-08-26):

See Asia/Ho_Chi_Minh for the source for most of rest of this data.

Methodology Note: The 1970 Rule

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