Timezone Data Distribution Service (tzdist) ----------------------------------------------------------- Timezone data is a critical element of computer systems and devices that make use of local time. In particular, it is critical to any calendaring and scheduling system, such as iCalendar (RFC 5545). Daylight saving time rules, which affect local UTC offsets, can change - sometimes at very short notice (just a few days) - as those rules are typically defined by political processes. Currently, there is no efficient, fast way to ensure that timezone data is updated in a timely and reliable manner on devices that need it. Timezone changes are often delivered as operating system updates, and are thus tied to release schedules that can trail the actual timezone changes by a significant period of time. A service is needed that can provide timely, reliable updates. One added benefit of such a service for iCalendar is the ability for calendaring clients and servers to agree on common, standard definitions of timezone data, removing the need to pass timezone data directly "by value" in iCalendar data. By allowing clients and servers to use timezones "by reference" significant network bandwidth and storage savings can be achieved. This working group will: - Define a timezone data distribution protocol that allows for efficient, timely updates of timezone data to be delivered to clients. This protocol must scale to vast numbers of clients, such as the potential "internet of things" devices, as well as to today's desktop computers and servers. - Define an extension to CalDAV (RFC 4791) to allow clients and servers to use timezones "by reference" to improve the efficiency of the overall protocol. The working group will use the following drafts as initial input for its work: draft-douglass-timezone-service-11 draft-daboo-caldav-timezone-ref-01 The working group will work under the following parameters: - The timezone data distribution protocol will initially be targeted at iCalendar-based clients, but should be flexible enough to deliver timezone data in other formats. - The timezone data will be based on the IANA Time Zone Database (http://www.iana.org/time-zones) but must be able to include any source of timezone data. - The timezone data distribution protocol should also offer an API to allow thin clients to easily make use of timezone data by querying for UTC offsets, offloading the sometimes complex work of expanding recurrence rules to the service. This API should be extensible to support other types of timezone operations in the future. - The timezone data distribution protocol will use current security protocols to protect the integrity and confidentiality of what is distributed. Even public timezone data can represent a significant privacy exposure when it is associated with the user or endpoint that is retrieving it. The following are Out of scope for the working group: - Any changes to the IANA timezone database process or infrastructure, as documented in RFC 6557, other than recommendations for possible security enhancements. - The naming process for timezone identifiers. The working group can consider adding a mechanism, such as a "namespace" prefix, to differentiate different timezone sources, but the nature of the timezone identifiers used will be controlled by the sources themselves. - Lookup protocols or APIs to map a location to a timezone.