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draft-ietf-dhc-dhcpv6-opt-timeconfig-02.txt
Does the IETF have a prefered format for specifying timezones in?
RFC 3339 seems relevant, but its more about specifying the time itself.
The DHC WG has a dhc option they want to advance that holds the
current timezone in it. E.g, excerting Section 5:
> 5. Timezone option
>
> The Timezone option is used by the server to convey client's timezone
> information to the client.
>
> The format of the Timezone option is:
>
> 0 1 2 3
> 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> | OPTION_TIME_ZONE | option-len |
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> | time-zone |
> | ... |
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>
> option-code: OPTION_TIME_ZONE (tbd)
>
> option-len: Length of the 'time-zone' field in octets
>
> time-zone: Time zone of the client in the format as explained below.
>
> Std[Offset[Dst[Offset],[Start[/Time],End[/Time]]]]
>
> where '[' and ']' enclose optional fields, '|' indicates choice
> of exactly one of the alternatives, ',' and '/' represent literal
> characters present in the string.
>
> If "Offset" is specified, then the time-zone is represented in the
> IEEE 1003.1 POSIX timezone format [3].
>
> Std Three or more octets for the standard timezone (Std).
> Any character (or case) except a leading colon, digits,
> comma, minus or plus sign is allowed. If the time-zone
> is not represented in IEEE 1003.1 POSIX timezone format [3],
> then Std is treated as the index to the timezone database,
> for example, a file name, from where additional information
> about the timezone may be obtained.
>
> Offset Indicates the value one must add to local time to
> arrive at UTC, of the form: [+|-]hh[:mm[:ss]]. Offset
> following Std is required, if the timezone is represented
> in IEEE 1003.1 POSIX timezone format. Digits are always
> interpreted as decimal number. If preceded by a '-', the
> timezone is east of the Prime Meridian, otherwise it is west
> ('+' is optional) The permissible values for hh[:mm[:ss]] are
> as follows:
>
> hh 0 <= hh <= 23
>
> mm 0 <= mm <= 60
>
> ss 0 <= ss <= 60
>
> Dst Three or more octets for the daylight savings timezone.
> If Dst is missing, then daylight savings time does not
> apply in this locale. If no Offset follows Dst, then
> Dst is assumed to be one hour ahead of standard time.
> Any character (or case) except a leading colon, digits,
> comma, minus or plus sign is allowed.
>
> Start Indicates the day of the year, in one of the formats
> indicated below, when to change to daylight savings time.
> The ``Time'' field (which follows immediately after a
> ``/'' character, if present) indicates when the change is
> made, in local time.
>
> End Indicates the day of the year, in one of the formats
> indicated below, when to change back from daylight
> savings time. The ``Time'' field (which follows
> immediately after a ``/'' character, if present)
> indicates when the change is made, in local time.
>
> Time Time has the same format as Offset, except that no
> leading ``-'' or ``+'' is permitted. The default is
> 02:00:00.
>
> The day of the year needs to be given in any of the following
> formats:
>
> Jn The julian day n, (1 <= n <= 365). Leap days are not
> counted.
>
> n Zero-based julian day, (0 <= n <= 365). Leap days are
> counted so it is possible to refer to Feb 29.
>
> Mm.n.d The ``d''th day, (0 <= d <= 6) of week ``n'' of month
> ``m'' of the year (1 <= n <= 5, 1 <= m <= 12, where week
> 5 means last ``d'' day in month ``m'' which may occur in
> either the fourth or the fifth week. Week ``1'' is the
> first week in which the ``d'' day occurs. Day ``0'' refers
> Sunday, day ``1'' refers Monday and so on.
>
> Examples:
>
> i) Indian Standard Time zone is represented as:
>
> IST-5:30
>
> Here, ``IST'' refers the standard timezone and ``-5:30'' is the offset.
> `-' sign in the offset says that the timezone is 5 hours and 30 minutes
> ahead of UTC. Absence of ``Dst'' says that daylight savings doesn't apply
> to this locale.
>
> ii) For Eastern USA time zone, 1986, the timezone string is as shown below:
>
> EST5EDT4,116/02:00:00,298/02:00:00
>
> It says:
>
> The standard time zone is in 5 hours behind UTC. The Daylight Savings
> Timezone is 4 hours behind UTC. Day light savings starts at 116 day, i.e.,
> April 27 02:00 AM standard time and ends at 298th day, i.e., October 26
> 02:00 AM daylight time.
>
> It can also represented as:
>
> EST5EDT,116/02:00:00,298/02:00:00
>
> Since no offset follows the ``Dst'', daylight savings time is 1 hour
> ahead of standard time, thus, it is 4 hours behind UTC.
>
> iii) Representing ii) in the non POSIX standard way is:
>
> America/New-York
>
> It says that the locale belongs to New-York timezone in America, which
> will be used as the index in to a timezone database to get more
> information of the timezone.
>
I'm struck that this document seems to be defining its own format
without really just deferring to some other standard document. Is this
right?
Thomas