ABOUT WHERORA
How WherOra calculates times
Quick answer
Every time on WherOra comes from the IANA time zone database, the public record of every place’s clock rules that phones, computers and browsers use. Live clocks are worked out in your browser from your device’s clock. The written answers on city, city-pair and time-zone pages are generated from the same database, checked by a second, separate program before they’re published, and re-checked after each clock change in the US, Europe and Australia. Last full check: .
Where the times come from
The IANA time zone database (also called tzdb or the Olson database) lists every time zone in the world, its offset from UTC and every clock change since 1970, plus announced future changes. Each place is identified by a name such as America/New_York or Asia/Kolkata. The volunteers who maintain it update it whenever a government changes its rules.
WherOra uses it in two ways:
- Live clocks and the converter use the copy built into your browser. If your browser is up to date, it has the current rules.
- Written answers, such as “Manila is 12 hours ahead of New York until November 1”, and the hour-by-hour tables are generated on our side (last run with database release 2026e), so they can be read without JavaScript.
Daylight saving time
Daylight saving rules are applied for the exact date you pick, not today’s date. That matters because countries change on different days: the US and Europe are a week or more apart each spring and autumn, and the southern hemisphere changes in the opposite direction. During those gap weeks, the gap between two cities can be an hour different from the rest of the season.
When clocks go forward, one hour doesn’t exist (for example 2:30 AM in New York on the second Sunday in March). When clocks go back, one hour happens twice. The converter tells you when you’ve picked either one.
Half-hour zones and abbreviations
Some places are 30 or 45 minutes off the hour, such as India (UTC+5:30) and Nepal (UTC+5:45). The converter works to the minute and the meeting planner moves in 15-minute steps, so :30 and :45 offsets come out exactly. See half-hour and 45-minute time zones.
Abbreviations such as EST, IST or CST are ambiguous: IST can mean India, Ireland or Israel, and many people write “EST” in summer when New York is on EDT. WherOra always names the place, and the time zone pages say which reading they use. See time zone abbreviations explained.
How the written answers are checked
City, city-pair, time-zone and converter pages, which state time differences, clock-change dates and call windows, are generated by one program and checked by another that works the numbers out a different way, using the ICU time zone engine that browsers such as Chrome use, instead of the one that wrote the page. Every badge, answer line, table row and quick answer has to match before anything is published. After publishing, the live pages are downloaded and checked again.
Because the answers mention the next clock change, they’re regenerated and re-checked after each change: in the US, Europe and Australia, each spring and autumn. Each of those pages shows the date of its last check.
What WherOra doesn’t do
- Public holidays aren’t checked by the world clock or meeting planner. The business days calculator uses its own holiday lists for 42 countries.
- Working hours default to 8 AM–5 PM local time, every day including weekends. You can change them, but they aren’t anyone’s real availability.
- “Daytime” means 7 AM–7 PM local time, not sunrise to sunset.
- Weather is a current estimate from Open-Meteo, not a forecast for a meeting time.
- Your device clock: if it’s wrong, the live clocks are wrong too. Conversions of a chosen date and time don’t depend on it.
Common questions
Where does WherOra get its time zone data?
From the IANA time zone database, the public list of every place’s clock rules that phones, computers and browsers use. Live clocks use the copy in your browser; written answers are generated from the same database on our side.
How does WherOra handle daylight saving time?
It applies each place’s rules for the exact date you choose, including the weeks when the US and Europe have changed on different dates, and it warns you when a time is skipped or repeated by a clock change.
How often are the time differences on WherOra checked?
Every city, city-pair, time-zone and converter page is regenerated and checked by a separate program after each clock change in the US, Europe and Australia, and the page shows the date of its last check.