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Time Zone Distribution Service

The Time Zone Distribution Service (TZDS), defined in RFC 7808, provides a standardized way to distribute time zone data over HTTPS.

Overview

TZDS allows clients to discover and retrieve authoritative time zone definitions from a trusted server. This solves the problem of clients having outdated or inconsistent time zone data.

Service Discovery

TZDS uses well-known URLs and WebFinger for discovery:

https://example.com/.well-known/timezone

Operations

List Time Zones

GET /tzdist/timezones

Returns a list of available time zone IDs.

Get Time Zone Data

GET /tzdist/timezones/America/New_York

Returns the time zone definition in iCalendar (VTIMEZONE) or other formats.

Sync Changes

Clients can use conditional requests (If-Modified-Since, If-None-Match) to efficiently check for updates without re-downloading unchanged data.

Benefits

  • Single source of truth — All clients use the same time zone data.
  • Timely updates — Changes propagate quickly when governments alter DST rules.
  • Reduced client complexity — Clients don’t need to bundle their own tzdata.
  • Consistent format — All clients receive VTIMEZONE in the same format.
Previous Sources of Time Zone Information
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