IANA Time Zone Database & Identifier Lookup
Look up official IANA time zone identifiers like 'America/Los_Angeles'. Get technical details, UTC offsets, and DST rules used by programmers and systems worldwide.
Select a timezone to view IANA database information
How the IANA Timezone Database Lookup Works
This tool searches the IANA Timezone Database (also known as tz database or zoneinfo) to find timezone information by location, timezone name, or UTC offset. The IANA database is the standard reference for timezone data used by operating systems, programming languages, and applications.
Each timezone entry includes the canonical name (like "America/New_York"), UTC offset, daylight saving time rules, and historical changes. The database tracks timezone information dating back to 1970 for most regions, with some data going back to the 1800s.
Information provided for each timezone:
- Canonical timezone name (e.g., "Europe/London")
- Current UTC offset (e.g., UTC+0 or UTC+1 for BST)
- Daylight saving time status and rules
- Country code and region
- Major cities in the timezone
- Historical timezone changes
- Abbreviations (GMT, BST, EST, EDT, etc.)
Search by city name, country, or partial timezone identifier. Results show matching timezones with their current offset and DST status. Click any timezone for detailed information including transition dates and historical data.
When You'd Actually Use This
Configuring server timezones
Setting up a server and need the correct timezone string? Search for your location, get the canonical IANA name (e.g., "America/Chicago" not "CST"). Use this in your server config for accurate time handling.
Debugging timezone bugs
Application showing wrong times? Look up the timezone your app is using. Verify the UTC offset and DST rules match expectations. Common issue: using abbreviations (EST) instead of IANA names.
Database timestamp troubleshooting
Timestamps stored in database look wrong? Check what timezone the database server uses. Compare with IANA data to understand if it's a storage issue or display issue.
Finding timezone for a location
User says they're in "Springfield" but there are 34 Springfields in the US. Search to see which timezones different Springfields are in. Disambiguate based on state or country context.
Understanding DST transition dates
When does DST start in Australia? (Hint: opposite of Northern Hemisphere.) Look up "Australia/Sydney" to see exact transition dates. Different countries change clocks on different dates.
Validating user timezone input
Building a form where users select their timezone? Use the database to validate entries. Ensure users pick valid IANA names, not made-up abbreviations that will break in production.
What to Know Before Using
Always use IANA names, not abbreviations."EST" is ambiguous - could mean US Eastern, Australian Eastern, or something else. "America/New_York" is unambiguous. Abbreviations also don't handle DST transitions correctly.
Timezone database versions matter.The IANA database is updated several times per year. Countries change DST rules, new timezones are added. Your system's timezone data might be outdated. Check the database version.
Some locations have changed timezones.Samoa skipped a day in 2011. Crimea changed from Ukraine to Russia timezone in 2014. Historical lookups show these changes. Current offset might differ from historical offset.
UTC offset isn't the same as timezone."UTC-5" could be America/New_York (EST), America/Bogota (Colombia), or America/Lima (Peru). These have different DST rules. Always use the full timezone name.
Pro tip: Store timestamps in UTC in your database, convert to local timezone only for display. This avoids timezone confusion and makes data portable across regions.
Common Questions
What's the difference between UTC and GMT?
For practical purposes, they're the same offset (UTC+0 = GMT). UTC is the modern standard based on atomic time. GMT is the older astronomical standard. Use UTC in technical contexts.
Why are some timezone names City/Country format?
IANA uses "Area/Location" format. Area is usually a continent or ocean. Location is a major city. "America/New_York" means the timezone used in New York within the Americas region.
How often does the timezone database update?
Typically 3-4 times per year. Updates include DST rule changes, new timezones, and historical corrections. Operating systems and languages release updates incorporating these changes.
What timezone should servers use?
Best practice: UTC. No DST complications, consistent across all servers regardless of physical location. Convert to local time only for user-facing displays.
Why does my timezone have multiple abbreviations?
Many timezones use different abbreviations for standard time and daylight time. EST (winter) and EDT (summer) for New York. The abbreviation changes when DST starts/ends.
Can a country have multiple timezones?
Yes, large countries span multiple timezones. USA has 9 timezones (including territories). Russia has 11. Australia has 3 main timezones plus special cases. Search by city for accuracy.
What about places that don't observe DST?
Many countries near the equator don't use DST - daylight hours don't vary much. Japan, China, India, and most African nations don't observe DST. Their UTC offset stays constant year-round.
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