Time Zones · IANA ↔ Windows
IANA to Windows time zone converter.
Type an IANA ID such as America/Toronto or a Windows name such as Eastern Standard Time. Get every matching mapping with its territory and the zone’s current UTC offset.
Look up a time zone
Mappings
Enter a time zone to look it up.
How the mapping works
Windows names its zones (for example “Eastern Standard Time”) differently from the IANA database that Linux, macOS, Java and browsers use (for example “America/Toronto”). The Unicode CLDR project publishes the table that links them. One Windows zone covers many IANA zones, so converting from IANA to Windows always gives one answer, while converting from Windows to IANA can give several.
Territory column and the default
Each row has a territory code. Territory 001 is the default: the single IANA ID CLDR picks to represent that Windows zone worldwide. A two-letter code such as CA or US lists the IANA IDs for that country, and ZZ is used for the generic Etc/GMT zones. Use the territory filter to narrow results. The name “Eastern Standard Time” also covers daylight saving time; it is the zone name, not a fixed offset.
Current UTC offset
The offset next to each IANA ID is computed in your browser with Intl.DateTimeFormat for the current moment, so it changes with daylight saving time. If your browser cannot supply it, no offset is shown. IANA IDs that CLDR does not list (older aliases such as Asia/Calcutta) return no match; try the current name.
Source and licence
Data: Unicode CLDR windowsZones.xml (main branch), fetched 30 September 2026. It lists 500 mappings for 139 Windows zones; mapping data version . © Unicode, Inc., used under the Unicode License. CLDR changes as Windows and tzdata change, so this snapshot can drift from newer releases.
All lookups run locally in your browser. Nothing you type is uploaded or stored.