Timezone Converter: One Time, Eight Cities, Step by Step
Reviewed by the OnlineFree.app team · Updated
Key points
- The Timezone Converter turns one date and time into local times for up to eight cities on a single screen.
- Offset badges are computed for the chosen instant, so they shift by an hour when either city changes to daylight saving time.
- Timezone abbreviations such as CST and IST are ambiguous; use IANA identifiers like Asia/Seoul instead.
- Everything runs in the browser through Intl, so no date, time or city selection ever leaves your device.
- Verify hard deadlines against the IANA time zone database, because an outdated browser can carry stale rules.
One time in, eight local times out
The Timezone Converter turns a single date and time from one source timezone into the matching local times for up to eight target cities, showing each result with its day-change badge and its distance from the source. You enter the wall-clock time once and the whole list recalculates as you type.
Results open with a UTC reference line: the same instant written as a UTC clock time and as an ISO 8601 string, ready to paste into a calendar entry, a scheduled job comment, or a config file. Beneath it, the source timezone sits pinned at the top of the list on a light background so you always have a baseline to compare against.
Each row shows the city or IANA zone name, the local time in large tabular digits, the date when it differs from the source date, and an offset badge such as +13h or −5h. A 12/24-hour switch changes only the display. Copy result exports the list as plain text, which is faster and less error-prone than retyping three cities into a chat message.
The calculation runs entirely in your browser through Intl, so nothing is transmitted, no account exists, and no history is stored. The Timezone Converter is deliberately one screen with no settings panel beyond that format switch.
How do you convert a time across timezones?
Start by setting the date and time. The field is prefilled with your current local time down to the minute, so for a quick check you press Now and skip typing entirely. For a real meeting, enter the exact wall clock in the source city — 09:00 on 10 March 2026, for example.
Confirm the From timezone. It defaults to the IANA zone the browser reports, which is correct most of the time and predictably wrong when you are on a VPN or travelling. Change it and every row updates immediately; there is no Convert button to press.
Add targets in the To timezones box, up to eight. The search matches IANA names and common aliases, so typing KST, JST or EST finds Asia/Seoul, Asia/Tokyo and America/New_York. Chips appear in the order you select them, and each one has its own remove control.
Read the list top-down. With 09:00 on 10 March 2026 from Asia/Seoul, New York shows 20:00 with a Previous day badge and −13h, London shows 00:00 at −9h, Sydney shows 11:00 at +2h, and Tokyo shows 09:00 at +0h. When the numbers look right, hit Copy result and paste them straight into the invite.
Why the offset badges change with daylight saving
Offsets are not constants. Each badge is computed for the exact instant you entered, using the IANA rules your browser carries, so the same city pair reads −14h in January and −13h after the US switch on 8 March 2026. A converter that stores a fixed difference will hand you the wrong hour twice a year.
Southern hemisphere zones flip the pattern. Sydney runs on AEDT (UTC+11) from early October to early April, so Seoul 09:00 maps to Sydney 11:00 in March but 10:00 in July, once Sydney is back on AEST (UTC+10). Checking a date six months out is worth the ten seconds it takes.
This is also why abbreviations are a trap. CST means UTC−6 in Chicago and UTC+8 in Shanghai; IST covers India, Ireland and Israel. The tool lists IANA identifiers precisely because they are unambiguous, and those are what belong in Cron entries and agent schedules.
Common mistakes in cross-timezone scheduling
Not every zone differs by whole hours. 09:00 UTC becomes 14:30 in Asia/Kolkata (+5:30) and 14:45 in Asia/Kathmandu (+5:45), and Adelaide sits at +9:30 for part of the year. Read the minutes the tool prints instead of rounding to the nearest hour, especially for standups with India-based teammates.
The time you type is a wall clock in the From zone, not in your own zone. A frequent error is pasting 15:00 while thinking in local time, then switching From to Europe/Berlin and wondering why everything jumped by five hours. Set the source zone first, then type the time.
Respect the eight-target cap. It exists so the result list stays on one screen; if you need a ninth city, copy the current list and swap a chip rather than opening a second tab and losing track of which list is current.
Limits of a single-instant converter
This is a single-instant converter by design. It does not find a meeting slot, poll attendees, remember favourite cities, or keep history between visits — each of those would turn a one-screen utility into an app. If you need recurring scheduling or voting, pair it with your calendar tool and use this page for the arithmetic.
Accuracy depends on the time zone data your browser ships. Browsers refresh it regularly, but a machine left unpatched for months can lag an IANA release, which matters at the edges of a DST transition. For hard deadlines, confirm against the IANA time zone database or an official clock such as time.gov.
Like the other browser-only utilities on OnlineFree.app, it needs no upload and no sign-up — the Free Logo Generator works the same way. Keep the tab pinned during planning season and it earns its place next to your calendar.
Frequently asked questions
Is the Timezone Converter free to use?
Yes. The Timezone Converter is free, needs no account, and imposes no usage limit beyond the eight-target cap on the results list. There is nothing to install: the page loads, you type a time, and the converted local times appear immediately. Because the calculation runs in the browser, repeated use costs nothing and leaves no history behind.
Does the Timezone Converter handle daylight saving time?
Yes. Every result is calculated for the exact instant you enter, using the IANA rules your browser carries, so a city that has switched to summer time shows the correctly shifted offset. The badge reflects that specific date rather than a fixed difference, which is why Seoul to New York reads −14h in January and −13h in April 2026.
How many timezones can I compare at once?
Up to eight target timezones, plus the source zone pinned at the top of the list as a baseline. The limit keeps results on a single screen without scrolling. If you need more cities, copy the current list with Copy result, then remove a chip to make room for the next one.
Is my date and time sent to a server?
No. The conversion uses the browser's built-in Intl API, so the date, the time and the selected cities never leave your device. There is no account, no saved history, and no request carrying your schedule. That makes it reasonable for internal release times, on-call rotations and other details you would rather not paste into a public form.
Can it convert dates in the past or far future?
Yes. The date field accepts past and future dates, and results follow the time zone rules known to your browser for that date. Conversions before 1970 and far-future dates depend on the tz database version your browser carries, so verify unusual dates against the IANA time zone database before relying on them.