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), moving their clocks forward by one hour for part of the year and back again — on dates that differ per country, and in opposite halves of the calendar north and south of the equator. 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.

Link to this tool with values filled in

Everything after the # stays in your browser — it is never sent to a server — so a link like this opens the tool ready to go without the values travelling anywhere but the address bar:

https://crunchify.net/tools/time-zone-converter#from=America%2FNew_York&to=Asia%2FTokyo&time=2026-09-14T15%3A00

Join the settings with &, and percent-encode each value so that spaces, newlines and any #, &, = or % inside one do not break the link. Leave a setting out to accept its default. If a setting is not recognised, the page says so rather than quietly ignoring it.

from (also source or origin) — text, up to 64 characters, required. The zone the given time is in, as an IANA id — e.g. `America/New_York`.
to (also target or dest) — text, up to 64 characters, required. The zone to convert into, as an IANA id — e.g. `Asia/Tokyo`.
time (also at, datetime or when) — text, up to 16 characters, defaults to nothing. The instant to convert, `YYYY-MM-DDTHH:MM`, read in the `from` zone. Omit for now.

How do I convert time zones?

Find the UTC offset difference between the two zones and add or subtract accordingly. For example, converting 3:00 PM New York (EST, UTC−5) to London (GMT, UTC+0): add 5 hours → 8:00 PM London. This tool handles daylight saving time automatically.

What is UTC and how does it relate to time zones?

UTC (Coordinated Universal Time) is the global time standard from which all time zones are defined as offsets. New York is UTC−5 in winter (UTC−4 in summer), London is UTC+0 (UTC+1 in summer), and Tokyo is UTC+9 year-round.

Why do time zone abbreviations like EST and IST cause confusion?

Abbreviations are not unique. IST can mean India Standard Time (UTC+5:30), Irish Standard Time (UTC+1), or Israel Standard Time (UTC+2). This tool uses IANA zone identifiers like America/New_York or Asia/Kolkata, which are unambiguous.

What is daylight saving time and which countries observe it?

Daylight saving time (DST) shifts clocks forward by 1 hour in spring and back in autumn, extending evening daylight. The US, Canada, most of Europe, and some other countries observe it. Japan, China, India, and most of Africa and Asia do not. Dates and rules vary by country.

What time zone should I use for scheduling international meetings?

UTC is the safest reference — it never observes daylight saving time and is unambiguous. Alternatively, agree on a single time zone for your team and always specify it explicitly (including the UTC offset) to avoid confusion around DST transitions.

Updated October 12, 2026

Time Zone Converter

Time zone conversions, pair by pair

How It Works