Timezone Converter

UTC (Coordinated Universal Time) is the primary international time standard against which all other time zones are measured. It is effectively the successor to GMT and does not change with Daylight Saving Time. All time zones are expressed as UTC+ or UTC− an offset. New York is UTC−5 in winter (EST) and UTC−4 in summer (EDT). Tokyo is always UTC+9. Servers, aviation, and international finance all use UTC internally to avoid ambiguity from DST transitions and local conventions.

DST shifts clocks forward by one hour in spring and back in autumn, changing the UTC offset of affected regions. The US switches on the second Sunday of March and first Sunday of November. Europe switches on the last Sunday of March and October. This means the offset between two cities can vary by 1–2 hours depending on the time of year. Example: New York to London is +5h in winter but only +4h in summer (because the US and UK switch DST at slightly different times). This converter uses your browser's timezone data to automatically account for current DST status.

London is UTC+1 in summer (BST) and UTC+0 in winter (GMT). New York is UTC−4 in summer (EDT) and UTC−5 in winter (EST). The time difference is typically 5 hours. The best overlap window is 9am–12pm New York time, which is 2pm–5pm London time — morning for New York, afternoon for London. Avoid scheduling after 5pm London time (12pm NY) because one party ends their workday. The gap narrows to 4h when the US has not yet switched to DST but the UK already has (late March to mid-April).

Los Angeles (Pacific Time) is UTC−8 in winter and UTC−7 in summer. London is 8h ahead in winter, 8h ahead in summer. Berlin and Paris are 9h ahead in winter, 9h ahead in summer. The overlap is extremely narrow. The best window is typically 9am–11am London / 12pm–2pm Berlin, which corresponds to 1am–3am Los Angeles — which is not viable. In practice, the only workable time is early morning Pacific: 8am–9am Pacific = 4pm–5pm London, 5pm–6pm Paris. One party always has an early morning or late afternoon call.

Many countries do not change their clocks at all: China (entire country stays UTC+8), Japan (UTC+9), India (UTC+5:30), most of Africa, most of Asia (including Singapore, Thailand, Indonesia, UAE, Saudi Arabia), Russia (abolished DST in 2014), and Iceland. In the United States, Arizona does not observe DST (except the Navajo Nation within Arizona). Hawaii also does not observe DST. When scheduling with these regions, the UTC offset stays constant year-round, making conversions simpler.

Step 1: Find the UTC offset of the source timezone. Step 2: Find the UTC offset of the target timezone. Step 3: Calculate the difference: target offset − source offset. Step 4: Add that difference to the source time. Example: Convert 3pm New York (UTC−5) to Tokyo (UTC+9). Difference = +9 − (−5) = +14h. 3pm + 14h = 5am next day. If the result exceeds 24h, subtract 24h and advance the date by one day. This calculator handles this automatically, including date changes.

The International Date Line (IDL) at roughly 180° longitude is where the calendar date changes. Crossing westward advances the date by one day; crossing eastward moves it back. This is relevant for conversions between the Americas and Asia-Pacific: when it is Monday evening in New York, it is already Tuesday morning in Tokyo. The result box in this converter always shows the correct date alongside the converted time, so you can see exactly if the date changes in the conversion.

India Standard Time (IST) is UTC+5:30 — a 30-minute offset from its neighbors. This was chosen so that the midday sun would fall as close as possible to solar noon across the geographic center of India. The alternative (UTC+5 or UTC+6) would give a large part of the country a solar noon very far from 12:00 pm on the clock. India does not observe DST, so IST stays at UTC+5:30 year-round. Nepal goes even further with UTC+5:45, the only 45-minute offset in the world. These non-standard offsets can complicate scheduling, as half-hour increments must be tracked.

The European Parliament voted in 2019 to abolish DST across the EU, but implementation has stalled due to disagreement over which permanent time to adopt (permanent summer time vs permanent winter time). If different EU countries choose different standards, borders between countries could have large permanent time differences. The arguments against DST include disruption to sleep patterns, negative health effects from the transitions, and reduced energy savings in modern homes. As of 2026, EU member states still switch twice per year while discussions continue.

Airlines always schedule departure and arrival times in local time at the respective airports. A flight from New York (UTC−5) departing at 7pm arriving in London (UTC+0) at 7am the next day is a 7-hour flight. Pilots and air traffic control communicate in UTC (called "Zulu time" in aviation). Flight durations are independent of time zones. A 14-hour flight from Los Angeles to Tokyo that departs at 11pm Monday arrives at 6am Wednesday local Tokyo time — crossing the Date Line advances the calendar date. Travelers often experience "day gain" flying westward and "day loss" flying east across the Pacific.