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@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@gmail.com> wrote:
>So, I mean, +7 is now more standard time with Hanoi than Ho Chi Minh City

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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@alum.mit.edu> wrote:
On Feb 17, 2019, at 6:40 PM, Tim Parenti <tim@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).