Time Zone Converter

How It Works

How It Works

This tool uses the browser's built-in Intl.DateTimeFormat API to convert times between IANA time zones — no external data or API calls required. The IANA Time Zone Database (used by your browser and operating system) contains the complete history of UTC offsets and daylight saving time rules for every time zone in the world.

UTC Offsets & DST

Every time zone has a UTC offset — the number of hours and minutes ahead of or behind Coordinated Universal Time (UTC). Many zones observe daylight saving time (DST), shifting clocks forward by one hour in summer. The offset shown always reflects the correct value for the selected date and time, so you never have to worry about whether DST is in effect.

Why "EST" is ambiguous

Common abbreviations like "EST" (Eastern Standard Time), "CST", and "IST" are not unique — IST can mean India Standard Time, Irish Standard Time, or Israel Standard Time. This tool uses IANA zone identifiers like America/New_York or Asia/Kolkata, which are unambiguous. The abbreviation is shown for quick reference, but the IANA name is the authoritative identifier.

Timeline visualization

The visual timeline shows where the selected time falls within a 24-hour day for each zone. Shaded regions represent approximate night hours (midnight–6 AM and 6 PM–midnight). The blue marker shows the selected time. This makes it easy to see at a glance whether a meeting time falls during business hours across all your zones.