TZ has this information in file backzone # From Paul Eggert (2014-10-11): # See Asia/Ho_Chi_Minh for the source for most of this data. Also, guess # (1) Cambodia reverted to UT +07 on 1945-09-02, when Vietnam did, and # (2) they also reverted to +07 on 1953-11-09, the date of independence. # These guesses are probably wrong but they're better than guessing no # transitions there. Zone Asia/Phnom_Penh 6:59:40 - LMT 1906 Jul 1 7:06:30 - PLMT 1911 May 1 7:00 - +07 1942 Dec 31 23:00 8:00 - +08 1945 Mar 14 23:00 9:00 - +09 1945 Sep 2 7:00 - +07 1947 Apr 1 8:00 - +08 1953 Nov 9 7:00 - +07 A good friend of mine born in 1951 in Phnom Pen is the adoptive daughter of late Cambodian ruler Prince Sihanouk. Being very interested in astrology, this friend of course much engaged in knowing the correct time zone for her birth. The information above would set it at 8h east of GMT for 1947 - 1953. My friend writes (and I have bolded the essential phrase): According to my father xxxx, during the French protectorate, Cambodia’s legal time was that of Hanoi. [..] My [adoptive] father Sihanouk confirmed the above in 2011 when I drafted my essay on King Sihanouk. I needed to ask him many questions, including details regarding our time zone, especially 5-6 August 1951. [...] 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. -- end quote ket In view of this, I would tend to eliminate the line 8:00 - +08 1953 Nov 9 Of course, it is here like in many other cases the question what TZ wants to represent: offical time maintained by the colonial administration, or 'time on the ground' used by the local population for their own records, like a royal birth event. I do not expect action by Paul Eggert, as this is only backzone data.Still. I consider it worthwile to be recorded in the TZ mailing ist history.