Date & Time Runs locally Ready to use Built-in examples No tracking

Time Zone Converter

Pick a source and target time zone, enter a date and local time, and get the target local time, UTC time, offsets and a comparison table of common time zones.

Booking a call across countries, reading an arrival time off a boarding pass, or judging whether it is too late to message someone — time-zone arithmetic is where daylight saving bites: the same pair of cities stands an hour apart in winter and in summer. Convert against a specific date rather than from memory and the answer is right for past and future alike; a reference table of common zones comes with it.

Daylight saving is the trap: New York, London and many others shift twice a year, so one offset does not hold all year — "New York is thirteen hours behind" is true in winter and wrong in summer, when it is twelve. This tool applies the offset in force on the date you enter, so historical and future conversions are both correct. Source and target local times, UTC and the offset applied are all shown.

—
—
—
—

How to use

  1. Choose the source and target time zones.
  2. Enter the date and the local time in the source zone.
  3. Read the target local time, the UTC time, the offset and the difference between the zones.
  4. Check the reference table of common zones, remembering the offset depends on the date.

How it works

The conversion principle

Conversion has two steps: subtract the source timezone's UTC offset from its wall-clock time to get the UTC instant, then restore it with the target timezone's offset. For example Beijing (UTC+8) at 20:00 on Sep 13 is UTC 12:00; New York is then UTC-4 (DST), so its local time is 08:00 — a real 12-hour gap, not the standard 13.

Handling daylight saving time

Daylight saving time (DST) is the biggest trap: the same city's UTC offset shifts by an hour across seasons. New York is UTC-4 in DST and UTC-5 in standard time; London is UTC+1 in DST and UTC+0 otherwise. This tool computes offsets live from the runtime's IANA timezone database for the specific date, so winter and summer results differ automatically — no manual addition needed.

Why IANA timezone names

This tool uses IANA "region/city" names (like Asia/Shanghai, America/New_York), not abbreviations like CST or EST, because abbreviations collide: CST can mean China Standard Time, US Central Time, or Cuba Standard Time — using abbreviations easily miscalculates.

Code example

JavaScript Formatting per time zone with Intl 

const d = new Date("2026-09-15T10:00:00+08:00");

new Intl.DateTimeFormat("en-US", {
  timeZone: "America/New_York",
  dateStyle: "short", timeStyle: "short"
}).format(d);   // "9/14/26, 10:00 PM" (EDT during daylight saving)

// Write time zone names the IANA way: Asia/Shanghai, Europe/London

Python Time zone conversion with zoneinfo 

from datetime import datetime
from zoneinfo import ZoneInfo

d = datetime(2026, 9, 15, 10, 0, tzinfo=ZoneInfo("Asia/Shanghai"))
d.astimezone(ZoneInfo("America/New_York"))
# 2026-09-14 22:00:00-04:00 (EDT, daylight saving)

# Python 3.9+ ships zoneinfo, no third-party library needed

FAQ

How is the time difference computed?

Subtract the two locations' UTC offsets. Beijing UTC+8 and New York DST UTC-4 differ by 12 hours; New York standard time UTC-5 makes it 13 hours. This tool uses the offsets for the actual conversion date, so the result varies by season.

Does daylight saving affect the result?

Yes, by a full hour. If the date falls within the DST window, the offset switches automatically: in 2026, New York on Sep 13 is UTC-4, but on Jan 15 it's UTC-5. Using the wrong season's offset is off by an hour.

Why does the gap between two cities change with the season?

Because they don't necessarily enter DST at the same time. China currently has no DST while the US and Europe do, so the China-US gap is 12 hours during DST and 13 during standard time; between Europe and America, differing switch dates create a roughly one-week "staggered" window where the gap briefly becomes 4 or 6 hours.

How far is Beijing time from UTC?

A fixed 8-hour difference: Beijing = UTC + 8, and China has no DST, so it's constant year-round. Beijing 20:00 is UTC 12:00, the most common reference conversion for scheduling international meetings.

How is cross-date conversion handled?

Fully automatically. For example Beijing 23:30 on Sep 13 becomes Tokyo (UTC+9) 00:30 the next day — the page shows 2026-09-14 00:30; in reverse to UTC it's 15:30 the same day. The table's "relative gap" is read with the date, so you don't see only the time and miss the day change.

Why isn't my city in the list?

The dropdown has a curated 21 common timezones for quick selection; conversion itself uses the IANA database covering 400+ zones. For a city outside the list, confirm its timezone name (most cities are named directly, like Europe/Lisbon).

Does timezone conversion need a network connection?

No. Timezone data ships locally with the browser/system's IANA database, and conversion makes no network requests, working offline. Because it relies on the local library, timezone rule updates (like a country dropping DST) take effect with system updates.