World Clock: Major City Time Zones
The world is divided into 24 main time zones. The table below shows UTC offsets in winter (standard time); many regions add +1 in summer (Daylight Saving Time).
Major Cities and UTC Offsets
UTC-8 Los Angeles (PST → PDT: +1 summer)
UTC-5 New York (EST → EDT: +1 summer)
UTC-3 Buenos Aires (no DST)
UTC-0 London (GMT → BST: +1 summer)
UTC+1 Paris, Berlin, Lagos, Accra
UTC+2 Cairo, Athens, Johannesburg
UTC+3 Moscow (no DST), Nairobi, Riyadh
UTC+5:30 Mumbai, Delhi
UTC+7 Bangkok, Jakarta
UTC+8 Beijing, Singapore, Perth
UTC+9 Tokyo, Seoul
UTC+10 Sydney (AEDT: +1 summer → UTC+11)
UTC+12 AucklandQuick Conversion Rule
From any city:
1. Look up its UTC offset
2. Add or subtract to get UTC
3. Then add destination's offset
New York (UTC-5) → Tokyo (UTC+9):
Difference = 9 - (-5) = +14 hours
9 AM New York = 11 PM Tokyo (same day)Check world clock: Free World Clock
World Clock Quick-Reference: Major Cities at UTC 12:00
| City | Time zone | UTC offset (standard) | Time at UTC 12:00 |
|---|---|---|---|
| Los Angeles | PST/PDT | −8 / −7 | 04:00 / 05:00 |
| New York | EST/EDT | −5 / −4 | 07:00 / 08:00 |
| São Paulo | BRT | −3 | 09:00 |
| London | GMT/BST | +0 / +1 | 12:00 / 13:00 |
| Paris/Berlin | CET/CEST | +1 / +2 | 13:00 / 14:00 |
| Dubai | GST | +4 | 16:00 |
| Mumbai/Delhi | IST | +5:30 | 17:30 |
| Singapore/HK | SGT/HKT | +8 | 20:00 |
| Tokyo/Seoul | JST/KST | +9 | 21:00 |
| Sydney | AEST/AEDT | +10 / +11 | 22:00 / 23:00 |
| Auckland | NZST/NZDT | +12 / +13 | 00:00 (next day) / 01:00 |
How World Clocks Work
A world clock displays the current local time in multiple cities simultaneously. Each city's time = UTC + its current offset (accounting for DST). The UTC offset changes twice a year for most countries observing Daylight Saving Time, but DST start/end dates differ by country and hemisphere (northern hemisphere springs forward in March; southern hemisphere in September/October). Some countries (Japan, China, India, Singapore) do not observe DST.
The International Date Line (IDL) runs roughly along the 180° meridian in the Pacific Ocean. Crossing it westward gains a day; crossing eastward loses a day. Samoa and Tonga are both UTC+13 on the west side of the IDL; Baker Island (uninhabited US territory) is UTC−12 on the east side — a potential 25-hour difference between the extreme ends of the time zone spectrum.
Common Mistakes
- Forgetting that DST dates differ between countries: In the 2–3 week windows when one country has switched but another hasn't, time differences shift by 1 hour. During late March, London may be UTC+0 while New York is still EST (UTC−5), making them 5 hours apart — but once New York switches to EDT, they're back to 4 hours apart.
- Not accounting for next-day crossings: When it is Monday morning in New York (8:00 AM EST), it is already Tuesday morning in Sydney (midnight AEDT). Scheduling Tuesday meetings by saying "let's talk Tuesday morning your time" requires specifying which Tuesday to avoid same-day/next-day confusion.
- Assuming business hours align: New York (9 AM–6 PM EST) and Singapore (9 AM–6 PM SGT) have zero business-hours overlap — Singapore is 13 hours ahead. The only feasible crossover is early Singapore morning / late New York evening.
Frequently Asked Questions
India Standard Time (IST, UTC+5:30) was established in 1947 as a political compromise — placing a single time zone across the entire subcontinent, with the offset splitting the difference between UTC+5 (western India) and UTC+6 (eastern India/Myanmar). Nepal (UTC+5:45) added a further 15-minute offset to differentiate itself from India while remaining close to local solar time. Both are examples of non-integer offsets chosen for political or geographic reasons.
The Prime Meridian (0° longitude) passes through the Royal Observatory, Greenwich, London — established as the international reference in 1884 at the International Meridian Conference, where 25 nations adopted Greenwich as the basis for a universal day. UTC (Coordinated Universal Time) is the successor to GMT and is maintained by the Bureau International des Poids et Mesures (BIPM) using a weighted average of ~450 atomic clocks worldwide, accurate to ~1 nanosecond per day.
Identify the UTC equivalent of standard business hours (9 AM–6 PM) for each participant's location. Overlap periods are the viable windows. Tools like Every Time Zone, World Time Buddy, or Calendly's time zone meeting planner display overlapping hours visually. For teams with no overlap (e.g., US East Coast + Singapore), consider rotating meeting times to share the burden of early/late calls rather than always requiring one location to join outside business hours.