What Is the IANA Time Zone Database?
Learn about the database behind city time zone names and why time conversion needs to follow rule updates.
The Rules Behind City Names
The IANA Time Zone Database records civil time rules for locations around the world. Identifiers such as Asia/Tokyo and America/New_York help software associate a location’s time zone with its historical and future rules.
Unlike storing a single UTC offset, a time zone identifier can express rules that change with the date, such as daylight saving time.
Why Updates Are Needed
Governments may adjust time zone or daylight saving policies, and the database is updated accordingly. The data version on your device, browser, and operating system can therefore affect the calculation for certain dates.
For important arrangements, or those near a policy change, keep your devices updated and reconfirm with official local information or the event organizer.
Put it into practice
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Pick cities and a date to easily compare times across time zones.
Open the time zone converter