[tz] [Tzdist-bis] [calsify] tzdist and IANA

Matt Johnson mj1856 at hotmail.com
Thu Jul 18 16:51:25 UTC 2019

AFAIK, tzdist isn't about setting the active time zone across computers.  It's about making sure those computers have reliable time zone data.

In Windows, tzutil.exe can list the time zones available, and can set the active time zone.  There are also other ways to set the active time zone across computers.  For example, if they are in a domain you can use group policy to update registry settings.  You could also use Set-TimeZone in powershell. See:  https://dennisspan.com/configuring-the-time-zone-and-code-page-with-group-policy

In Windows, time zone data updates (including Microsoft and IANA time zone data) are handled through Windows Update.  On Linux, IANA data is typically pushed out via a "tzdata" package.  The benefit of a tzdist-like system would simply be that time zone updates could be pushed out more rapidly than these other update processes typically take.  In other words, it is simply an out-of-band, purpose-built update process.  Such a process would be helpful when governments do not allow enough lead time for updates to get created and distributed, such as described in my blog post: https://codeofmatt.com/on-the-timing-of-time-zone-changes<https://codeofmatt.com/on-the-timing-of-time-zone-changes/>


From: tz <tz-bounces at iana.org> on behalf of Luigi Rosa <lists at luigirosa.com>
Sent: Thursday, July 18, 2019 6:27 AM
To: tz at iana.org <tz at iana.org>
Subject: Re: [tz] [Tzdist-bis] [calsify] tzdist and IANA

Daniel Migault wrote on 18/07/2019 15:07:
>      >> Wouldn't it be nice to have an infrastructure similar to what the NTP
>      >> pool provides for time synchronization?

My two cents of an admin of hosts (mainly Windows) that travel back and forth
thru the seven seas (namely Cruise ships).

Short version: TZ sync is a pain in the arse.

Long version.
You cannot use UTC for all the hosts because, for instance, some of them show
information to the guests or are used to manage crew shifts (always expressed in
ship time).

On some ships the so called "master clock" has two NTP servers: one "classic"
UTC and the other with ship time.

We cannot use ship time NTP server because NTP clients (correctly) assume that
NTP is about UTC, while the local time is just a "logical view" of NTP. If we
sync Windows hosts with ship time the result is a mess (somebody said "Kerberos"?).

We concocted a simple way to sync TZ between Windows hosts.

The "TZ Server" runs the command

tzutil /g > c:\tz\tz.txt

C:\tz is shared as TZ

Every client issue the commands

set /p TZ=<<file://>\\TZSERVER\TZ\TZ.TXT
tzutil /s "%TZ%"

The procedure is tested on Win2016, 2012R2 and Win10

Detailed info in my blog article:

The original is in Italian:



+--[Luigi Rosa]--
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