[tz] Add new timezone for Hanoi Capital, Vietnam

KP khaiphan9x at gmail.com
Mon Feb 18 20:31:45 UTC 2019

I will mention some of the following stages:

- GMT+0: July 1, 1906 to April 30, 1911 (Indochina)

- GMT+7: May 1, 1911 (Indochina)

- GMT+8: 23:00 December 31, 1942 (Indochina)

- GMT+9: 23:00 on March 14, 1945 (Empire of Vietnam)

- GMT+7: September 2, 1945 (Democratic Republic of Vietnam) and July 1,
1955 (État du Viêt-Nam)

- GMT+8: 23:00 on January 1, 1960 (Republic of Vietnam) and GMT+7: January
1968 (Democratic Republic of Vietnam)

- GMT+7: June 13, 1975 (Republic of South Vietnam)

Thus, Vietnam time has been different in 1945 (Saigon/HCMC does not exist)
no longer in Indochina time.
As mentioned, a small change can also lead to a timezone.
It is possible to create a time zone for Hanoi from here according to the
historical facts I mentioned. You can learn more documents to validate this

Vào 2:43, Th 3, 19 thg 2, 2019 Hans-Joerg Happel <happel at audriga.com đã

> Dear KP,
> to summarize and perhaps resolve some confusion, I see two points here:
> >I would like to suggest adding a timezone for Hanoi or changing the name
> >from Asia/Ho_Chi_Minh to Asia/Hanoi as the official timezone for Vietnam.
> 1) tzdb does not aim to provide or define a list of the current "official
> timezone" for any country.
> In contrast, it provides a list of official (and sometimes even
> inofficial?) time zones which have been valid for some certain area of the
> world from 1970 till now. Vietnam (VN) overlaps with two such areas (via
> zone1970.tab as Tim pointed out): one labeled "Asia/Ho_Chi_Minh" and one
> labeled "Asia/Bangkok", the latter covering a larger part of Indochina
> including Hanoi.
> Forming one single "official timezone" for Vietnam (or renaming
> "Asia/Ho_Chi_Minh" to "Asia/Hanoi") would not be correct, as from the
> 1970-based perspective of tzdb, the Ho Chi Minh area (South VN) and the
> Hanoi area (North VN) had different time zone rules (until 1975, as pointed
> out).
> So any system using tzdb data will require the implementer (or end user)
> to choose if either "Asia/Ho_Chi_Minh" or "Asia/Bangkok" should be used for
> any particular entered data, as it can make a difference for certain
> calculations, due to different time zone rules in the past.
> The special case here is that there are no more differences between South
> + North VN time zones since 1975. In contrast to countries with multiple
> time zones that are still differing today (e.g., Australia, Russia or the
> US), one can thus argue that a distinction between South + North VN time
> may not be practically relevant for many implementations, as it would only
> make a difference for data between 1970-1975.
> Any system implementer is free in offering end users a single "Vietnam
> time", which e.g., internally maps to tzdb's "Asia/Ho_Chi_Minh". However,
> this is up to any implementer and not to tzdb.
> 2) tzdb time zone names should rather be considered as (technical)
> identifiers. So "Asia/Bangkok" (and its links such as "Asia/Phnom_Penh")
> refer to the same set of time zone rules shared by that area.
> This is not imply any Thai influence or "leadership" regarding this time
> zone, but is a mere convention. If the Cambodian or Vietnamese government
> would deviate their time zone rules anytime soon, tzdb would automatically
> create separate identifiers - but only for "technical", not for political
> reasons!
> So tzdb's time zone "names" should not be taken too literal, as they do
> not intend to be used as user-facing labels. Software implementers can
> still apply localization and aliases on top of those identifiers.
> It's part of the truth though, that tzdb names might surface to end users
> at certain points. It's however not necessarily tzdb to blame for this.
> (Both points based on my current understand of the state of affairs -
> please feel free to correct me if I am wrong in some point)
> Best,
> Hans-Joerg
> On 18.02.19 11:21, KP wrote:
> Thank you from the above friends, so you can see that the +7 time zone of
> Hanoi has a longer history and maybe 1 time zone is Asia/Hanoi. If you live
> in Vietnam, you will clearly see the difference in time in Hanoi and HCMC,
> in the future when Vietnam is more developed, it may be necessary to adjust
> the HN and HCMC timezone. Paul Eggert, I know that there must be some rules
> for forming time zones. However, I see many exceptions such as Shanghai and
> Beijing, there are many other places that I have not mentioned. I think
> Hanoi too full of criteria for a time zone, or you can consider it an
> exception. Why not?
> Vào 16:48, Th 2, 18 thg 2, 2019 Phake Nick <c933103 at gmail.com đã viết:
>> Tz database does not deal with official timezone name. The time used in
>> Vietnam being named Hanoi time doesn't make it more Hanoi than Ho Chi Minh
>> as both should be using the same UTC+7 now. The different was in 1970s. If
>> your software is expected to show official timezone name used in a region,
>> then it's supposed to translate Asia/Ho_Chi_Minh into "Hanoi Time"
>> On 2019-2-18 Mon 14:48, KP <khaiphan9x at gmail.com> wrote:
>> >So, I mean, +7 is now more standard time with Hanoi than Ho Chi Minh City
>> -----
>> The thing is, the timezone history of Hanoi and Ho Chi Minh look like
>> this:
>> Hanoi: 1970-2019 UTC+7
>> Ho Chi Minh: 1970-1975 UTC+8 1975-2019 UTC+7
>> Bangkok: 1970-2019 UTC+7
>> Thus you can see the timezone history of Hanoi match the timezone history
>> of Bangkok from 1970 till now, while it doesn't match for HCM City.
>> On 2019-2-18 Mon 16:53, Guy Harris <guy at alum.mit.edu> wrote:
>>> On Feb 17, 2019, at 6:40 PM, Tim Parenti <tim at timtimeonline.com> wrote:
>>> > As was discussed on the original thread in October 2014,
>>> pre-unification time in Hanoi matches Asia/Bangkok since 1970
>>> By which you presumably mean "from 1970 to 1976", because
>>> "pre-unification time" ends when North and South Vietnam were reunified in
>>> 1976.
>>> > and thus is already considered covered by the database.
>>> If *post*-unification time - which is post-1970 - doesn't match
>>> Asia/Bangkok, then Asia/Bangkok should not be used for any part of Vietnam;
>>> there should be one or more Asia/{whatever} for Vietnam from 1970 to the
>>> present.
>>> If Vietnam's pre-unification offset or rules were different between the
>>> north and the south from 1970 to 1976, then "one or more" means "at least
>>> two", e.g. Asia/Hanoi and Asia/Ho_Chi_Minh (even if it was called Saigon in
>>> 1970).
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