Question 1

How does this time zone converter handle DST?

Accepted Answer

We use the browser's built-in Intl.DateTimeFormat with the full IANA timezone database, which knows every historical and future DST rule change for 400+ zones. When you pick a date and source zone, we look up the actual UTC offset at that exact instant — including for past dates when DST rules were different. We also flag the twice-a-year ambiguous local times (spring-forward gaps and fall-back overlaps) that break naive converters.

Question 2

What is a spring-forward gap and a fall-back overlap?

Accepted Answer

In the spring, clocks jump from 02:00 to 03:00 (in most zones), so local times between 02:00 and 03:00 never occur — that's a gap. In the autumn, clocks fall back from 02:00 to 01:00, so local times between 01:00 and 02:00 occur twice (once in DST, once in standard) — that's an overlap. This tool explicitly detects and warns about both. For overlap times, we use the DST (earlier) interpretation by default.

Question 3

How does the half-hour and 45-minute zones work?

Accepted Answer

Not all time zones are whole-hour offsets. India (IST) is UTC+5:30, Nepal (NPT) is UTC+5:45, the Chatham Islands (CHAST) is UTC+12:45, and a handful of others use 30- or 45-minute offsets. This tool correctly handles all of them because we compute offsets minute-by-minute from the IANA database rather than rounding to whole hours.

Question 4

Can I convert one time to multiple zones at once?

Accepted Answer

Yes. Enter your source date, time and zone once, then add as many target zones as you like — New York, London, Berlin, Mumbai, Tokyo, Sydney, etc. — and we show every target's wall-clock, UTC offset, abbreviation and DST flag side-by-side. You can also see a difference summary like 'Mumbai is 9h 30m ahead of New York right now'.

Question 5

What extra features does this tool have versus others?

Accepted Answer

(1) City/zone autocomplete mapped to IANA ids (400+ zones, 200+ cities). (2) DST-aware conversion for any past/future date using Intl + IANA database. (3) One source instant → many target zones simultaneously. (4) UTC offset, abbreviation (IST/PST/etc.) and DST-active flag per zone. (5) Spring-forward gap warning + fall-back overlap detection with explicit disambiguation. (6) Live 'now' mode with one-click copy ISO/UTC. (7) Difference summary ('X is 9h 30m behind Y'). (8) Half-hour and 45-minute zone support (IST, NPT, CHAST). (9) Shareable URL encoding source + targets + instant (fragment, never sent to server). (10) localStorage history (max 20, metadata only). (11) Historical DST rule changes respected. (12) Mobile-first stacked cards with offset badges.

Question 6

Is my data sent anywhere?

Accepted Answer

No. All timezone math runs locally via Intl.DateTimeFormat with the IANA database bundled in your browser. History is stored in localStorage on this device only and contains metadata (zone ids + instant), never your notes.

Time Zone Converter

Target zones (3)

Source (America/New_York)

Targets

How to use

Target zones (3)

Source (America/New_York)

Targets