How a Time Zone Converter Works
A time zone converter takes a date and time in one part of the world and shows you what that same instant looks like on the clock in another part of the world. It seems simple — just add or subtract a fixed offset — but the reality is much messier. Daylight saving time, half-hour and quarter-hour offsets, historical changes to time zone definitions, and the difference between a region and its current rules all combine to make this one of the trickiest pieces of math in everyday computing. This converter handles it correctly by relying on the IANA time zone database that ships with every modern browser.
Why IANA Zones Beat Fixed Offsets
You will see two ways to refer to a time zone in the wild. The first is a fixed UTC offset like UTC-5 or GMT+9. The second is an IANA zone name like America/New_York or Asia/Tokyo. Fixed offsets are always wrong somewhere — they cannot account for daylight saving transitions, regional differences within a UTC band, or historical rule changes. IANA zone names point to a complete dataset of every rule that has ever applied in that region, including the dates daylight saving begins and ends each year. This converter uses IANA names exclusively so its results are correct year-round, including across the spring-forward and fall-back transitions.
How to Convert a Time
Pick the source zone from the From dropdown — the zones are grouped by continent for easy browsing. Enter the source date and time, or click Use current time to fill in the current moment. Add one or more destination zones in the lower section. The converter shows the wall-clock time in each destination zone along with the day of the week, so you can spot the cases where converting across the international date line produces a result on a different calendar day.
Quick Presets
The most common conversions for an English-speaking audience have one-click presets. EST to PST is the classic US coast-to-coast jump. EST to GMT covers transatlantic calls with London. EST to IST is critical for working with teams in India. EST to JST handles the early-morning Tokyo standup. Click any preset to populate both sides of the converter and see the result instantly.
World Clock
The world clock at the bottom of the page shows the current time in eight major cities around the globe and updates once per second. This is useful as a quick reference to confirm your colleague's working hours before sending a Slack message, or to plan when a market opens, or just to know whether it is reasonable to call someone right now. The clock relies entirely on your computer's idea of what time it is — if your local clock is wrong, the world clock will be wrong too.
Daylight Saving Caveats
During the few weeks each year when the United States, the European Union, and Australia have not all transitioned to or from daylight saving on the same day, the offset between any two zones can shift unexpectedly. The converter handles this correctly because it uses each zone's own rules — but if you are scheduling a recurring meeting that needs to feel "the same" to all attendees year-round, be aware that fixed-time meetings will appear to drift by an hour twice a year for some participants.
Frequently Asked Questions
Why does the result change at night even though I changed nothing?
The world clock updates every second to stay current. The conversion result only changes when you change the input — but if you used Use current time, the source field updates with each click.
Are odd time zones supported?
Yes — the converter uses the full IANA database, so half-hour offsets like India (UTC+5:30) and quarter-hour offsets like Nepal (UTC+5:45) work correctly without any special configuration.
Does it know the difference between EST and EDT?
Yes. The IANA name America/New_York automatically applies EST in winter and EDT in summer based on the date you enter, so you never have to think about which abbreviation to pick.
This time zone converter is completely free, runs in your browser using built-in browser APIs, and does not send any data anywhere. Bookmark it for the next time you need to schedule across time zones.