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<p>Dear KP,</p>
<p>to summarize and perhaps resolve some confusion, I see two points
here:</p>
<p>>I would like to suggest adding a timezone for Hanoi or
changing the name<br>
>from Asia/Ho_Chi_Minh to Asia/Hanoi as the official timezone
for Vietnam.</p>
<p><br>
</p>
<p>1) tzdb does not aim to provide or define a list of the current
"official timezone" for any country.</p>
<p>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.</p>
<p>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).</p>
<p>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.</p>
<p>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.</p>
<p>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.<br>
</p>
<p><br>
</p>
<p>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.</p>
<p>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!<br>
</p>
<p>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.<br>
</p>
<p>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.</p>
<p>(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)</p>
<p>Best,<br>
Hans-Joerg<br>
</p>
<div class="moz-cite-prefix">On 18.02.19 11:21, KP wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAN9+tTsEYi3D66XXB1JE9FO=QPA5WHBoAfSdrs-CNx8NtofPcw@mail.gmail.com">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<div dir="auto">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?</div>
<br>
<div class="gmail_quote">
<div dir="ltr">Vào 16:48, Th 2, 18 thg 2, 2019 Phake Nick <<a
href="mailto:c933103@gmail.com" moz-do-not-send="true">c933103@gmail.com</a>
đã viết:<br>
</div>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir="auto">
<div dir="auto">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"</div>
<div dir="auto"><br>
</div>
<div dir="auto">On 2019-2-18 Mon 14:48, KP <<a
href="mailto:khaiphan9x@gmail.com" rel="noreferrer
noreferrer noreferrer noreferrer" target="_blank"
moz-do-not-send="true">khaiphan9x@gmail.com</a>>
wrote:</div>
<div dir="auto">>So, I mean, +7 is now more standard time
with Hanoi than Ho Chi Minh City</div>
<div dir="auto"><br>
</div>
<div dir="auto">-----</div>
<div dir="auto">The thing is, the timezone history of Hanoi
and Ho Chi Minh look like this:</div>
<div dir="auto">Hanoi: 1970-2019 UTC+7</div>
<div dir="auto">Ho Chi Minh: 1970-1975 UTC+8 1975-2019 UTC+7</div>
<div dir="auto">Bangkok: 1970-2019 UTC+7</div>
<div dir="auto"><br>
</div>
<div dir="auto">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.</div>
<br>
<div class="gmail_quote" dir="auto">
<div dir="ltr">On 2019-2-18 Mon 16:53, Guy Harris <<a
href="mailto:guy@alum.mit.edu" rel="noreferrer
noreferrer noreferrer noreferrer" target="_blank"
moz-do-not-send="true">guy@alum.mit.edu</a>> wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">On Feb
17, 2019, at 6:40 PM, Tim Parenti <<a
href="mailto:tim@timtimeonline.com" rel="noreferrer
noreferrer noreferrer noreferrer noreferrer"
target="_blank" moz-do-not-send="true">tim@timtimeonline.com</a>>
wrote:<br>
<br>
> As was discussed on the original thread in October
2014, pre-unification time in Hanoi matches Asia/Bangkok
since 1970<br>
<br>
By which you presumably mean "from 1970 to 1976",
because "pre-unification time" ends when North and South
Vietnam were reunified in 1976.<br>
<br>
> and thus is already considered covered by the
database.<br>
<br>
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.<br>
<br>
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).</blockquote>
</div>
</div>
</blockquote>
</div>
</blockquote>
<p><br>
</p>
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