Metazone timestamps

Matt Johnson (AZURE) via CLDR-Users cldr-users at
Wed Nov 1 14:47:40 CDT 2017

Ticket filed here.  Thanks.

From: Yoshito Umaoka [mailto:yoshito_umaoka at]
Sent: Wednesday, November 1, 2017 8:31 AM
To: Matt Johnson (AZURE) <matt.johnson at>
Cc: cldr-users at
Subject: Re: Metazone timestamps

> In<>
> there is an example:
> <timezone type="America/Indiana/Knox">
>   <usesMetazone to="1991-10-27 07:00" mzone="America_Central"/>
>   <usesMetazone to="2006-04-02 07:00" from="1991-10-27 07:00"
> mzone="America_Eastern"/>
>   <usesMetazone from="2006-04-02 07:00" mzone="America_Central"/>
> </timezone>
> It also states: “Note that the dates and times are specified in UTC,
> not local time.”


> As currently presented, they appear to be local time.  Is there a
> reason these aren't just expressed as ISO 8601 timestamps with a
> trailing Z?  In other words:  “1991-10-27T07:00Z”
> Note that ISO 8601 allows for a space instead of a T, so these
> timestamps are ISO 8601 compliant, but also that in absence of a Z
> or an offset they are required to be interpreted as local time.

I guess the original author/designer of this data did not really care about ISO 8601 conformance.

> I’ve certainly made this mistake in interpreting them before.  I’m
> sure others have as well.  Would it be possible to change this in a
> future version?

I actually felt the same when I started maintaining the data.
Personally, I'm fine to change the date/time string to be ISO UTC time format (and use the default date/time separator - 'T'), then update the spec to explain it's ISO 8601 UTC date/time format explicitly.

But, this change may break existing code utilizing this data, so we probably need to discuss this in CLDR TC.

Anyway, can you file a CLDR ticket?

> Thanks,
> Matt Johnson
> Microsoft
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