Question 1

Which time zones can I add?

Accepted Answer

Any IANA zone - more than 400 of them, covering every country and region. Search by city (Tokyo, New York, São Paulo) or zone identifier (Asia/Tokyo, America/New_York). Daylight saving and historical zone changes are handled by the browser's underlying tzdata.

Question 2

Why is the time slightly off?

Accepted Answer

The clock relies on your OS time, which should sync via NTP. If your laptop has been offline for a long time or has a misconfigured time zone, the displayed values shift accordingly. Sync your system clock first if accuracy matters.

Question 3

Are daylight saving transitions handled?

Accepted Answer

Yes. The browser's Intl/IANA tzdata knows DST rules per zone, including historical changes. Note that some countries change DST rules occasionally (e.g. Mexico abolished DST in 2022); make sure your browser is recent enough to have current data.

Question 4

Can I see UTC and the local zone difference?

Accepted Answer

Yes. Each city card shows local time plus the offset from UTC (e.g. UTC+9 for Tokyo, UTC-5 for New York). DST shifts are reflected automatically - New York shows UTC-4 in summer, UTC-5 in winter.

Question 5

Will it work for meeting scheduling?

Accepted Answer

It shows current time in each zone, which is the most common use case. For finding overlapping working hours, look at all the card columns at once. For 'what does 3 PM in NYC convert to in Tokyo' use a dedicated meeting planner - this is a clock, not a meeting planner.

Question 6

Can I save my favorite cities?

Accepted Answer

Yes - most builds save your selection to localStorage, so the same browser shows the same list next visit. Cross-device sync needs an account, which a basic clock doesn't have.

Question 7

Is anything uploaded?

Accepted Answer

No. The clock reads system time and IANA zone data from the browser. Nothing is logged or transmitted.

Koidu - World Clock

City Information