Time zone converter and world clock
Pick the places you deal with, then slide the bar until you find an hour that is not the middle of the night for anyone. Nothing is looked up online — your browser already knows every time zone.
- Runs entirely in your browser
- Works offline
- No upload
- No sign-up
- No watermark
Loading the tool…
How it works
- Add the cities you need. The first one is the reference; drag the bar to move its time.
- Read each city’s local time, the day difference (+1 / −1), and the shaded 9–18 working band.
- Set any city as the reference, remove the ones you do not need, or copy the whole list as text.
Why nothing is uploaded
Every operation on this page is done by code running inside your browser tab, using the same engine that renders web pages. The file is read from disk into your tab’s memory, transformed there, and written back out as a download. It is never sent anywhere — not to us, not to a third party.
Verify it yourself
- Open your browser’s developer tools (F12) and select the Network tab.
- Load your file and run the tool.
- The only requests you will see fetch the tool’s own code — and, for a few heavy tools, their open-source engine from a public CDN — plus one small page-view ping to loreatec.jp (page address and title, nothing more). None of them carry your file.
Frequently asked questions
Does it work offline?
Yes. Every modern browser carries the full time-zone database, including the daylight-saving rules, so the conversion is done on your device. Once the page has loaded, it keeps working with no connection.
Are daylight-saving changes handled?
Yes. The time shown for each city uses that zone’s rules for the exact date on the bar, so if you move the date across a clock change, the offset changes with it. That is the main thing a converter has to get right.
What do the +1 and −1 mean?
They mean the city is on the next or the previous calendar day compared with your reference city. When you schedule across a big gap — Japan and the US west coast, say — it is easy to book a meeting on the wrong day; this makes the day difference obvious.
Why is my choice of cities remembered?
The list is kept in your browser’s local storage, so the tool opens with the same cities next time. It is stored only on your device and is never sent anywhere. Clearing your browser data removes it.