About

Where the times come from

No offset or clock-change date is typed in by hand. The server computes them from the IANA time zone database built into PHP – currently version 2026.5. Your browser keeps the clocks ticking with its own copy of the same database (Intl.DateTimeFormat), so the time on the page follows your device clock. If the two database versions differ (for example right after a country changes its rules), results may briefly disagree – the newer database wins.

A zone in the IANA database is an area where clocks have agreed since 1970. That is why Argentina has a dozen zones with a single offset: they differ in history, not in today's time. Zone names such as “Central European Time” come from ICU/CLDR.

The map, day and night

Countries are coloured by the current UTC offset of their capital; countries with several offsets are striped, and their own pages show the zones on a map of regions. Each region gets the zone where most of its people live (based on GeoNames cities and zone.tab reference points), with a few manual corrections – zone borders don't always follow state or province lines, so treat it as an approximation.

The day/night line is computed in your browser from the Sun's position (declination and hour angle from simplified astronomical formulas, accurate to about 0.1°) and refreshed every minute; the shadow also covers civil, nautical and astronomical twilight. Sunrise and sunset on city pages are computed by PHP (date_sun_info) from the city's coordinates and may differ from almanacs by a minute or two.

Cities

The city list comes from GeoNames (cities15000): all capitals, cities over 400,000 people, regional capitals over 150,000, the three largest cities of every country and the largest city of every IANA zone. Districts and suburbs closer than 10 km to a larger city were skipped. Polish names are the preferred names from the GeoNames alternate names; population figures are as in GeoNames and may be outdated.

Time difference pages work for any pair of cities, but only pairs of the 36 biggest hubs are offered to search engines – for everything else, use the meeting planner.

Sources and licences

• Time zones: IANA Time Zone Database – public domain; in PHP as timezonedb, in browsers as part of ICU.
• Cities, names, continents: GeoNames – CC BY 4.0. The data was selected and processed (city selection, names, zone assignment to regions).
• Country and region borders: Natural Earth – public domain (WorldMap/RegionMap asset).
• Zone names and date formats: Unicode CLDR via ICU – Unicode licence.
• Fonts: Manrope and JetBrains Mono – SIL Open Font License 1.1, served from this domain.

Texts and page layout by the site's editors. The data may contain errors – double-check the time of an important flight or meeting with the source.

Privacy

This site uses no cookies. Visit statistics are collected by Matomo in cookieless mode – no identifiers stored in your browser and nothing shared with advertisers. Your browser stores only two settings locally (localStorage), and only if you change them yourself: the 12/24-hour time format and the light or dark theme (the switches in the header; in automatic mode no theme is stored). They stay on your device and are never sent to the server. Cities in the meeting planner live only in the page address.

Contact form

• Contact form. When you write to us (contact page), we process your name or nickname, e-mail address and message, as well as the name of the site and the page from which the message was sent. The message is delivered by e-mail to contact@ominuvo.com.
• Purpose and legal basis: replying to your message – on the basis of the consent you give in the form (art. 6(1)(a) GDPR); protecting the form against spam and abuse – on the basis of the controller's legitimate interest (art. 6(1)(f) GDPR). Providing the data is voluntary, but without it we cannot reply.
• Spam protection: we store the sender's IP address only as a hash (the address cannot be recovered from it) for the message limit, and delete it after an hour. The form uses no cookies.
• Recipients and retention: the data is stored by our hosting and e-mail provider, which processes it only on our behalf; we do not sell it or share it with anyone else. We keep the correspondence for as long as needed to reply, and then for no longer than 12 months, unless longer retention is required by law or for the defence of legal claims.
• Withdrawing consent: at any time, by writing to contact@ominuvo.com. Withdrawing consent does not affect the lawfulness of processing before the withdrawal. You also have the right to data portability.
• Controller and your rights: the data controller is the owner of the Ominuvo service (contact: contact@ominuvo.com). You have the right to access, rectify and erase your data, to restrict its processing, to object, and to lodge a complaint with a supervisory authority – in Poland the President of the Personal Data Protection Office (UODO).