Timezone Service Protocol

Timezone information, in general, combines a Universal Coordinated Time (UTC) offset with daylight saving time (DST) rules. Timezones are typically tied to specific geographic and geopolitical regions. Whilst the UTC offset for particular regions changes infrequently, DST rules can change frequently and sometimes with very little notice (sometimes hours before a change comes into effect). Calendaring and scheduling systems, such as those that use iCalendar, as well as operating systems, critically rely on timezone information to determine the correct local time. As such they need to be kept up to date with changes to timezone information. To date there has been no fast and easy way to do that. Timezone data is often supplied in the form of a set of data files that have to be "compiled" into a suitable database format for use by the client application or operating system. In the case of operating systems, those changes often only get propagated out to client machines when there is an operating system update and those may not be frequent enough to ensure accurate timezone data is always in place. This specification defines a timezone service protocol that allows for fast, reliable and accurate delivery of timezone information to client systems. This protocol is based on HTTP using a REST style API. This specification does not specify the source of the timezone information. It is assumed that a reliable and accurate source is available. One such source is the Olson database - see for a proposal to host the data in IANA. This specification does not address the need for global timezone identifiers for timezone data.

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in . This document uses XML DTD fragments (, Section 3.2) as a purely notational convention. The namespace "urn:ietf:params:xml:ns:timezone-service" is reserved for the XML elements defined in this specification, its revisions, and related specifications. XML elements defined by individual implementations MUST NOT use the "urn:ietf:params:xml:ns:timezone-service" namespace, and instead should use a namespace that they control. When XML element types in the "urn:ietf:params:xml:ns:timezone-service" namespace are referenced in this document outside of the context of an XML fragment, the string "TZ:" will be prefixed to the element types.

The following terms with the given meanings are used throughout this document. A server implementing the Timezone Service Protocol defined by this specification; A globally unique name which identifies timezone information.

The overall process for the delivery of timezone information can be visualized via the diagram shown below.

The overall service is made up of several layers: Individuals, governments or organizations which provide information about timezone definitions to the publishing process. There can be many contributors. Publishers aggregate information from contributors, determine the reliability of the information and, based on that, generate timezone definitions. There can be many publishers, each getting data from many different contributors. In some cases a publisher may choose to "re-publish" data from another publisher. Servers which obtain and then provide the timezone data from publishers and make that available to other servers or clients. There can be many root providers. Root providers can choose to supply timezone data from one or more (or all) publishers. Servers which handle the bulk of the requests and reduce the load on root servers. These will typically be simple caches of the root server, located closer to clients. For example a large Internet Service Provider (ISP) may choose to setup their own local provider to allow clients within their network to make requests of that server rather than making requests of servers outside their network. Local servers will cache and periodically refresh data from the root servers. Applications, operating systems etc., that make use of timezone data and retrieve that from either root or local providers. Some of those layers may be coalesced by implementors. For example, a vendor may choose to implement the entire service as a single monolithic virtual server with the address embedded in distributed systems. Others may choose to provide a service consisting of multiple layers of providers, many local servers and a small number of root servers. This specification is only concerned with the protocol used to exchange data between providers and from provider to client. This specification does not specify how contributors pass their information to publishers, nor how those publishers vet that information to obtain the level of trust required of the final result.

The default format for returning timezone definitions is the iCalendar data format. In addition, the iCalendar-in-XML representation is also available.

Timezone identifier aliases map one timezone identifier onto another. Aliases allow the timezone service to map old timezone specifications onto a new specification. A timezone alias can be provided in the timezone data and should be mapped on to the target timezone specification. This can be done by the client or by the server. The client can request that aliases be returned along with summary information when listing timezones provided by the timezone service. Clients can then map received timezone identifiers on to the target perhaps avoiding a fetch of the target specification. Alternatively, the client can just fetch the timezone specification by supplying the timezone identifier alias. The service will return the target timezone specification and it is the clients' responsibility to notice that the returned data has a different timezone identifier to that requested. The client SHOULD store the mapping so that future requests for that aliased identifier do not result in an unnecessary fetch.

Over time zone timezone definitions are replaced by others, but are maintained for historical purposes. Often times clients are only concerned with timezone whose definitions are valid for current and future dates and times. When listing timezones provided by a timezone service, the server will by default only provide the list of "active" timezones. However, clients can use a request parameter to have the server also return details for "inactive" timezones.

When presenting timezones to users, clients will typically want to display a "presentation" name for the timezone, rather than the timezone identifier. In that case, clients would want a "presentation" name localized for the current user. The timezone service can be requested to return localized names for timezones by the addition of request parameters. Names in multiple lanaguages can be returned in a single request.

Timezone information is generally slow moving. However, changes need to be distributed in a timely manner. The list of timezones that change from even year-to-year will typically be relatively small. When listing timezones, a global timestamp is returned by the server, and that can be used later by clients to determine if any "substantive" change has occurred in the timezone data. Clients can use a conditional list request, supplying a previous global timestamp value, to limit the results to timezones which have changed in a "substantive" manner since that previous global timestamp. This allows clients to cache the last global timestamp and to periodically poll the server for possible changes. Clients SHOULD limit automatic polling to no more than once a week. A "substantive" change is one which affects the calculated onsets for a timezone or a change to the region it covers. Changes to properties such as description are not treated as a "substantive" change.

Determining timezone offsets at a particular point in time is often a complicated process as the rules for daylight saving time can be complex. To help with this, the timezone service provides an operation that allows clients to request the server to expand a timezone definition into a set of "observances" over a fixed period of time. Each of these observances describes a local onset time and UTC offsets for the prior time and the observance time. Together, these provide a quick way for "thin" clients to determine an appropriate UTF offset for an arbitrary date without having to do full timezone expansion themselves.

All servers MUST deliver timezone information for all timezones. This means that any client API implementation can go to a single server to get all timezone information. In turn, any server can refresh any of the data from any other server - though the root servers may provide the most up-to-date copy of the data. All service providers MUST deliver functionally equivalent data for all timezones. This ensures that all parties in a contract agree on the UTC time. Service providers (or publishers) may choose to map a particular region on to a different timezone identifier to correct a deficiency in the original timezone specification. With opaque timezone identifiers this remapping may be short lived and the mapping can revert to the original identifier once the deficiency has been addressed by the publisher.

This protocol is designed to be extensible through a standards based registration mechanism (see ). It is anticipated, that other useful timezone operations will be added in the future (e.g., mapping a geographical location to timezone identifiers, getting change history for timezones). To that end, servers MUST return a description of their capabilities. This will allow clients to determine if new features have been installed and, if not, fall back on earlier features or disable some client capabilities.

The interactions are simple HTTP requests. Most security considerations are already handled adequately by HTTP. However, given the nature of the data being transferred and the requirement it be correct all interactions between client and server SHOULD use an HTTP connection protected with TLS as defined in . The HTTP GET request method is used, with information passed in request parameters. The "action" request parameter specifies which operation is to take place, other request parameters act as arguments to that operation.

Client implementations need to either know where the timezone service is located or discover it through some mechanism. To use a timezone service, a client needs an FQDN, port and HTTP request-URI path.

defines a DNS-based service discovery protocol that has been widely adopted as a means of locating particular services within a local area network and beyond, using SRV RR records. This can be used to discover a service's FQDN and port. This specification adds two service types for use with SRV records: Identifies a Timezone server that uses HTTP without transport layer security (). Identifies a Timezone server that uses HTTP with transport layer security (). Clients MUST honor "TTL", "Priority" and "Weight" values in the SRV records, as described by .

Example: service record for server without transport layer security _timezone._tcp SRV 0 1 80 tz.example.com.

Example: service record for server with transport layer security _timezones._tcp SRV 0 1 443 tz.example.com.

When SRV RRs are used to advertise a timezone service, it is also convenient to be able to specify a "context path" in the DNS to be retrieved at the same time. To enable that, this specification uses a TXT RR that follows the syntax defined in Section 6 of and defines a "path" key for use in that record. The value of the key MUST be the actual "context path" to the corresponding service on the server. A site might provide TXT records in addition to SRV records for each service. When present, clients MUST use the "path" value as the "context path" for the service in HTTP requests. When not present, clients use the ".well-known" URI approach described next.

Example: text record for service with transport layer security _timezones._tcp TXT path=/timezones

A "well-known" URI is registered by this specification for the Timezone service, "timezone" (see ). This URI points to a resource that the client can use as the initial "context path" for the service they are trying to connect to. The server MUST redirect HTTP requests for that resource to the actual "context path" using one of the available mechanisms provided by HTTP (e.g., using a 301, 303, 307 response). Clients MUST handle HTTP redirects on the ".well-known" URI. Servers MUST NOT locate the actual timezone service endpoint at the ".well-known" URI as per Section 1.1 of . Servers SHOULD set an appropriate Cache-Control header value (as per Section 14.9 of ) in the redirect response to ensure caching occurs or does not occur as needed, or as required by the type of response generated. For example, if it is anticipated that the location of the redirect might change over time, then a "no-cache" value would be used. To facilitate "context path's" that might differ from user to user, the server MAY require authentication when a client tries to access the ".well-known" URI (i.e., the server would return a 401 status response to the unauthenticated request from the client, then return the redirect response only after a successful authentication by the client).

A Timezone server has a "context path" that is "/servlet/timezone". The client will use "/.well-known/timezone" as the path for the service process after it has first found the FQDN and port number via an SRV lookup or via manual entry of information by the user from which the client can parse suitable information. When the client makes its initial HTTP request against "/.well-known/timezone", the server would issue an HTTP 301 redirect response with a Location response header using the path "/servlet/timezone". The client would then "follow" this redirect to the new resource and continue making HTTP requests there.

All requests require the "action" request parameter to define what action is required of the server. Servers MUST support the following request parameters.

action Specify the action to be carried out. Any IANA registered operation name.

format Specify the format for the timezone data returned by the server as a standard MIME media-type. If absent the iCalendar format will be returned with the timezones contained within a "VCALENDAR" object (i.e., a default media-type of "text/calendar"). A MIME media-type. The server MUST support the following values: Return data as "VTIMEZONE" components embedded in a "VCALENDAR" object as per . Return data using the XML representation of iCalendar data as per XML-Calendar.

changesince Specify the timestamp for a conditional timezone list request in order to restrict the result to timezones changed since the given timestamp (see ). An iCalendar "DATE" or "DATE-TIME" value. Typically a value returned in a previous request's "dtstamp" XML element.

start Specify the inclusive start of a period. An iCalendar "DATE" or "DATE-TIME" value. If an 'end' request parameter is also present, then both the 'start' and 'end' values MUST be of the same "DATE" or "DATE-TIME" value types.

end Specify the exclusive end of a period. An iCalendar "DATE" or "DATE-TIME" value. If a 'start' request parameter is also present, then both the 'start' and 'end' values MUST be of the same "DATE" or "DATE-TIME" value types.

lang Specify the language in which locale specific values are to be returned. e.g., when fetching aliases, if a language is specified, only aliases for that language will be returned. The value is a standard ISO3036 letter code + country code.

returnaliases If present, indicates that timezone identifier aliases should be returned in the timezone list. When fetching the list of timezones the default action is to omit aliases. The inclusion of this parameter causes timezone aliases to be returned in the list (see ). This parameter takes no value.

returnall If present indicates that all timezones should be returned. When fetching the list of timezones the default action is to omit inactive timezones. The inclusion of this parameter causes inactive timezones to be returned in the list (see ). This parameter takes no value.

tzid This parameter is used to identify a timezone to be targeted by an operation. A timezone identifier name. In some cases the special value "*" is used to indicate that all timezones should be matched.

Servers MUST support the following operations.

capabilities This operation returns the capabilities of the server, allowing clients to determine if a specific feature has been deployed and/or enabled. REQUIRED, value MUST be "capabilities" An XML document containing a "capabilities" element as the root element.

In this example the client requests the server capabilities. > Request << GET /?action=capabilities HTTP/1.1 Host: tz.example.com >> Response << HTTP/1.1 200 OK Date: Wed, 4 Jun 2008 09:32:12 GMT Content-Type: application/xml; charset="utf-8" Content-Length: xxxx list List timezone identifiers and localized forms

lang false true Specify desired localized form(s)

changedsince false false Limit result to timezones changed since the given date

returnall false false If present inactive timezones will be returned.

get Returns one or more timeszones as specified by the tzid parameter.

format false false text/calendar application/calendar+xml Specify required format for timezone.

lang false true Specify desired localized form(s)

tzid true true Specify desired timezone identifiers

expand Expands the specified timezone(s) into local onset and UTC offsets

tzid true true Specify desired timezone identifiers

start false false Specify start of the period of interest. If omitted the current year is assumed.

end false false Specify end of the period of interest. If omitted the current year + 10 is assumed.

capabilities Gets the capabilities of the server ]]>

list This operation lists all timezone identifiers, in summary format, with optional localized data. In addition, it returns a timestamp which is the current server global last modification value. REQUIRED, value MUST be "list" OPTIONAL, but MAY occur multiple times. Specifies the language or languages for localized information. OPTIONAL, but MUST occur only once. If present, indicates that timezone aliases should be returned in the list. OPTIONAL, but MUST occur only once. If present, indicates that all, including inactive, timezones should be returned in the response. The TZ:inactive XML element will flag those timezones no longer in use. OPTIONAL, but MUST occur only once. If present, limits the response to timezones changed since the given timestamp. An XML document containing a "timezone-list" element as the root element.

In this example the client requests the timezone identifiers and in addition requests that the US-English local names be returned. > Request << GET /?action=list&lang=en_US HTTP/1.1 Host: tz.example.com >> Response << HTTP/1.1 200 OK Date: Wed, 4 Jun 2008 09:32:12 GMT Content-Type: application/xml; charset="utf-8" Content-Length: xxxx

20091011T093211Z

America/New_York

20090917T013934Z

America/New_York

... ]]>

get This operation returns a timezone. Clients must be prepared to accept a timezone with a different identifier if the requested identifier is an alias. REQUIRED, value MUST be "get" OPTIONAL, but MUST occur only once. Return information using the specified media-type. In the absence of this parameter, the value "text/calendar" MUST be assumed. OPTIONAL, but MAY occur multiple times. If present, specifies the language or languages for localized information. REQUIRED, but MAY occur multiple times. Identifies the timezone for which information is returned. Alternatively, if a single value of "*" is given, returns information for all timezones. The "*" option will typically be used by servers that wish to retrieve the entire set of timezones supported by another server to re-synchronize their entire data cache. Clients will typically only retrieve individual timezone data on a case-by-case basis. A document containing all the requested timezone data in the format specified.

In this example the client requests the timezone with a specific timezone identifier to be returned > Request << GET /?action=get&tzid=America/New_York &format=text/calendar HTTP/1.1 Host: tz.example.com >> Response << HTTP/1.1 200 OK Date: Wed, 4 Jun 2008 09:32:12 GMT Content-Type: text/calendar; charset="utf-8" Content-Length: xxxx BEGIN:VCALENDAR ... BEGIN:VTIMEZONE ... END:VTIMEZONE END:VCALENDAR ]]>

expand This operation expands the specified timezone(s) into a list of onset start date/time and offset. REQUIRED, value MUST be "expand" REQUIRED, but MAY occur multiple times. Identifies the timezones for which information is returned. The value "*", which has a special meaning in the "get" operation, is not supported by this operation. OPTIONAL, but MAY occur multiple times. If present, specifies the language or languages for localized information. OPTIONAL, but MUST occur only once. If present, specifies the start of the period of interest. If omitted, the current year is assumed. OPTIONAL, but MUST occur only once. If present, specifies the end of the period of interest. If omitted, the current year + 10 is assumed. An XML document containing a "timezones" element as the root element.

In this example the client requests a timezone in the expanded form. > Request << GET /?action=expand&tzid=America/New_York HTTP/1.1 Host: tz.example.com >> Response << HTTP/1.1 200 OK Date: Wed, 4 Jun 2008 09:32:12 GMT Content-Type: application/xml; charset="utf-8" Content-Length: xxxx 20091011T093211Z America/New_York Gregorian Daylight 20080309T070000Z

-0500

-0400

Standard 20081102T070000Z

-0400

-0500

Daylight 20090308T070000Z

-0500

-0400

... ]]>

XML elements used by this specification are defined here.

capabilities urn:ietf:params:xml:ns:timezone-service Root element encapsulating timezone service capabilities information. This defines the root (top-level) element used as the container for capabilities information.

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operation urn:ietf:params:xml:ns:timezone-service Element encapsulating timezone operation description This defines the element used as the container for information defining an operation and its parameters.

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action urn:ietf:params:xml:ns:timezone-service Define name of an action Specify name of an operation's action.

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description urn:ietf:params:xml:ns:timezone-service A description. This element specifies a description that refers to the enclosing element.

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accept-parameter urn:ietf:params:xml:ns:timezone-service Element defining a timezone operation parameter This defines the name, type and characteristics of an operation parameter.

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required urn:ietf:params:xml:ns:timezone-service Specify if timezone method parameter is required Specify if timezone method parameter is required. Values of "true" or "false" are used.

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multi urn:ietf:params:xml:ns:timezone-service Specify if timezone method parameter is multi-valued Specify if timezone method parameter is multi-valued. Values of "true" or "false" are used.

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value urn:ietf:params:xml:ns:timezone-service Allowed values for a parameter. This element specifies the allowed values for a parameter. If present, only the set of valus specified will be allowed by the server.

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timezone-list urn:ietf:params:xml:ns:timezone-service Root element encapsulating timezone list information. This defines the root (top-level) element used as the container for timezone listing.

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dtstamp urn:ietf:params:xml:ns:timezone-service Provide a timestamp value. Provides the UTC date and time when a substantive change was made to the timezone data.

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summary urn:ietf:params:xml:ns:timezone-service Defines a timezone summary. This defines the element that provides summary information for a timezone in the timezones list.

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tzid urn:ietf:params:xml:ns:timezone-service The identifier for the timezone. The text value is the identifier of the timezone being referred to.

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last-modified urn:ietf:params:xml:ns:timezone-service Provide a timestamp value. Provides the UTC date and time that the timezone data was last modified.

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local-name urn:ietf:params:xml:ns:timezone-service A localized name for the timezone. Defines one or more localized names that are used when a timezone identifier needs to be presented to a user. The xml:lang attribute is used to indicate the language associated with each value. If multiple names are provided for the same locale the preferred name should be flagged with the "PREF=true" attribute. In the absence of any indication the client is free to choose.

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alias urn:ietf:params:xml:ns:timezone-service An alternative identifier for the timezone. Defines alternative identifiers that can be used for the timezone. This feature allows mapping of old identifiers onto new.

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timezones urn:ietf:params:xml:ns:timezone-service Root element encapsulating expanded timezone information. This defines the root (top-level) element used as the container for expanded timezone data.

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tzdata urn:ietf:params:xml:ns:timezone-service Encapsulates expanded timezone information. This element specifies expanded timezone data for the range specified in a request.

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calscale urn:ietf:params:xml:ns:timezone-service Identifies the calendar system for the timezone data. The calendar system defines how rules, dates and times are to be interpreted. Currently only the value "Gregorian" is supported, referring to the Gregorian calendar scale. If this element is not present in its normal context, then the value "Gregorian" MUST be assumed.

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observance urn:ietf:params:xml:ns:timezone-service Provides data for a single observance period for a timezone. In an expanded timezone, the observance element specifies a single timezone observance.

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name urn:ietf:params:xml:ns:timezone-service Name for the observance. This element specifies which timezone observance is being referred to. Typically this will be either "Standard" or "Daylight".

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onset urn:ietf:params:xml:ns:timezone-service Local time onset of the observance. The onset element defines the local time at which the observance takes effect.

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utc-offset-from urn:ietf:params:xml:ns:timezone-service UTC offset before the start of the observance. The utc-offset-from element defines the UTC offset in hours and minutes before the start of this observance.

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utc-offset-to urn:ietf:params:xml:ns:timezone-service UTC offset after the start of the observance. The utc-offset-to element defines the UTC offset in hours and minutes at and after the start of this observance.

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Following is the XML schema for the timezone service responses.

The calendar system defines how rules, dates and times are to be interpreted. Currently only the value "Gregorian" is supported, referring to the Gregorian calendar scale. If this element is not present in its normal context, then the value "Gregorian" MUST be assumed. Provides the UTC date and time when a substantive change was made to the timezone data. Provides the UTC date and time that the timezone data was last modified. Defines one or more localized names that are used when a timezone identifier needs to be presented to a user. The xml:lang attribute is used to indicate the language associated with each value. If multiple names are provided for the same locale the first is considered the preferred name. The onset element defines the local time at which the observance takes effect. The text value is the identifier of the timezone being referred to. The utc-offset-from element defines the UTC offset in hours and minutes before the start of this observance. The utc-offset-to element defines the UTC offset in hours and minutes at and after the start of this observance. Defines alternative identifiers that can be used for the timezone. This feature allows mapping of old identifiers onto new. This defines the name, type and characteristics of an operation parameter. The element used as the container for information defining an operation and its parameters. . The root (top-level) element used as the container for capabilities information. This defines the element that provides summary information for a timezone in the timezones list. This defines the root (top-level) element used as the container for a timezone listing. In an expanded timezone, the observance element specifies a single timezone observance. This element specifies expanded timezone data for the range specified in a request. This defines the root (top-level) element used as the container for expanded timezone data. ]]>

Timezone data is critical in determining local or UTC time for devices and in calendaring and scheduling operations. As such, it is vital that a reliable source of timezone data is used. Servers providing a timezone service MUST support HTTP over Transport Layer Security (TLS) (as defined by ) with a valid certificate. Clients and servers making use of a timezone service SHOULD use HTTP over TLS and verify the authenticity of the service being used before accepting and using any timezone data from that source. Clients that support transport layer security as defined by SHOULD try the "_timezones" service first before trying the "_timezone" service. Clients MUST follow the certificate verification process specified in . A malicious attacker with access to the DNS server data, or able to get spoofed answers cached in a recursive resolver, can potentially cause clients to connect to any server chosen by the attacker. In the absence of a secure DNS option, clients SHOULD check that the target FQDN returned in the SRV record matches the original service domain that was queried. If the target FQDN is not in the queried domain, clients SHOULD verify with the user that the SRV target FQDN is suitable for use before executing any connections to the host.

This document uses one new URN to identify a new XML namespace for the response data used in this specification, and defines a new registry of "actions" for the timezone service protocol, and defines a "well-known" URI using the registration procedure and template from Section 5.1 of , and creates two new SRV service label aliases.

Registration request for the timezone service namespace: URI: urn:ietf:params:xml:ns:timezone-service Registrant Contact: See the "Authors' Addresses" section of this document. XML: None. Namespace URIs do not represent an XML specification.

This section defines the process to register new or modified timezone service operations with IANA.

The IETF will create a mailing list, timezone-service@ietf.org, which can be used for public discussion of timezone service operations proposals prior to registration. Use of the mailing list is strongly encouraged. The IESG will appoint a designated expert who will monitor the timezone-service@ietf.org mailing list and review registrations. Registration of new timezone service operations MUST be reviewed by the designated expert and published in an RFC. A Standard Tracks RFC is REQUIRED for the registration of new timezone service operations. A Standard Tracks RFC is also REQUIRED for changes to operations previously documented in a Standard Tracks RFC. The registration procedure begins when a completed registration template, defined in the sections below, is sent to timezone-service@ietf.org and iana@iana.org. The designated expert is expected to tell IANA and the submitter of the registration within two weeks whether the registration is approved, approved with minor changes, or rejected with cause. When a registration is rejected with cause, it can be re-submitted if the concerns listed in the cause are addressed. Decisions made by the designated expert can be appealed to the IESG Applications Area Director, then to the IESG. They follow the normal appeals procedure for IESG decisions.

An operation is defined by completing the following template. The name of the operation. This is also the value of the "action" parameter used in timezone service requests. A general description of the operation, its purpose, etc. A list of allowed request parameters, indicating whether they are "REQUIRED" or "OPTIONAL" and whether they can occur only once or multiple times. The nature of the response to the HTTP request, e.g., what format the response data is in.

An operation parameter is defined by completing the following template. The name of the parameter. A general description of the parameter, its purpose, etc. The format of the parameter value, or an indication that the parameter has no value.

The IANA is requested to create and maintain the following registries for timezone service operations with pointers to appropriate reference documents.

The following table is to be used to initialize the operations registry. Operation Name Status Reference capabilities Current RFCXXXX, list Current RFCXXXX, get Current RFCXXXX, expand Current RFCXXXX,

The following table is to be used to initialize the parameters registry. Parameter Status Reference action Current RFCXXXX, changedsince Current RFCXXXX, end Current RFCXXXX, format Current RFCXXXX, lang Current RFCXXXX, returnaliases Current RFCXXXX, returnall Current RFCXXXX, start Current RFCXXXX, tzid Current RFCXXXX,

timezone IETF. This RFC.

IANA is requested to add "timezone" and "timezones" service labels as aliases for "http" and "https" respectively.

The authors would like to thank the members of the Calendaring and Scheduling Consortium's Timezone Technical Committee and the following individuals for contributing their ideas and support: Bryan Keller, Ciny Joy, Arnaud Quillaud, Jose Edvaldo Saraiva. The authors would also like to thank the Calendaring and Scheduling Consortium for advice with this specification.