Convert time zones in plain English

Write the time and both places the way you'd say them, like 6pm PST in Tokyo, and Omacus answers on the same line: 10:00 AM JST (next day). No menus, no picking cities from a list.

Omacus is a free notepad calculator for Linux, macOS and Windows. Each line you type is calculated as you type it, so a page of meeting times reads like a note to yourself, with every answer lined up on the right.

Quick examples

Answers were calculated on 16 October 2026. Omacus always uses the date you're typing on, so daylight saving is right for today.

Three ways to name a place

Abbreviations

PST, EST, CST, MST, IST, UTC, GMT, BST, CET, EET, JST, KST, SGT, HKT, AEST, NZST and more. The summer versions (PDT, EDT, CEST, AEDT) work too, and so do the short forms PT, ET, CT and MT.

Cities

Every city in the IANA time-zone database, plus common names like San Francisco, Seattle, NYC, Boston, Austin, Bangalore and Mumbai. Multi-word names just work.

Countries and zone names

Countries with a single zone (Japan, Germany, France, the UK, India, the UAE) work by name. For anywhere else, the full IANA name is always understood.

Daylight saving, handled

People say "PST" all year, even in summer when California is really on PDT. Omacus reads an abbreviation as the place it belongs to, so PST means "Pacific time" and you get the right answer in any month. The result shows the abbreviation that's actually in effect:

That's also why EST above came back as EDT: on the day these answers were calculated, New York was on daylight time.

Next day, previous day

When the converted time falls on another date, Omacus says so, which is easy to miss when you do the math in your head.

On a specific date

Planning ahead? Add a date. Clocks change on different days around the world (the US and Europe switch a week apart in spring and autumn), so a meeting next month can land at a different hour than one today. Write the date the way you would: on Dec 1, 1 December 2026, 2026-12-01, tomorrow, Friday or next Monday. The answer shows the date it falls on there.

From now, and clock math

Count forward from now with in 90 minutes or 3 hours from now, and add in a place to see it there. Clock times take minutes and hours too, which is handy for agendas: 3pm + 45 min.

Ways to write the time

12-hour or 24-hour, with or without minutes, upper or lower case: 3pm, 3:30 PM, 9:30 am, 15:30, noon and midnight. Use in or to between the places.

Label your lines

Words before the time are treated as a label, so a list of meetings stays readable:

The time right now

Write time in Tokyo or now in London for the current time there. A time without a zone means your own: 3pm in London converts 3pm where you are.

Planning a meeting across zones

Because every line keeps its answer, a sheet is a quick way to find a time that works for everyone. Try one time, read down the column, adjust:

See more sheets like this on the use cases page.

Questions

Does it handle daylight saving time?

Yes. Abbreviations like PST and EST are read as their region (Pacific, Eastern), and the conversion uses the rules in effect on the day you type, from the IANA time-zone database built into the app.

Does it need the internet for time zones?

No. Time zones are calculated entirely on your computer; the only requests Omacus makes are for exchange rates and a daily check for new versions.

Which time zone abbreviations does it know?

The common ones for North America, Europe, Asia and Australia, such as PST, EST, CST, MST, GMT, BST, CET, EET, IST, JST, KST, SGT, HKT, AEST and NZST, plus their daylight versions. Any city or IANA zone name works too.

Can I convert a time on a specific date?

Yes. Add the date anywhere before in: 3pm PST on Dec 1 in London, 9am PST tomorrow in Tokyo or next Monday 10am ET in Berlin. Daylight saving is applied for that date, and the answer shows the date there.

IST could mean India or Israel. Which one is it?

India Standard Time. For Israel, write a city instead: 3pm PST in Jerusalem.