Convertisseur de fuseaux horaires

Timezone Converter

Converting times between time zones is something most people need daily — scheduling a meeting with a London colleague, calling family in Tokyo, or watching a live stream from Sydney. Every time zone is defined as an offset from UTC (Coordinated Universal Time), and the converter uses those offsets to calculate the exact difference between any two zones, including zones with half-hour and 45-minute offsets. The result also reflects whether daylight saving time is currently active in each location.

How Timezone Conversion Is Calculated

The formula is straightforward: take the source time, convert it to UTC by applying the source offset, then apply the target offset to get the local time in the destination zone. For example, 3:00 PM EST (UTC-5) converts to UTC as 8:00 PM, which is then converted to JST (UTC+9) as 5:00 AM the next day. The tool handles DST automatically — when EST becomes EDT (UTC-4 in summer), the offsets update accordingly without any manual adjustment.

Worked Examples

Example 1 — New York to London A 9:00 AM EST Monday meeting in New York falls at 2:00 PM GMT the same day (EST is UTC-5, GMT is UTC+0, difference is +5 hours). During British Summer Time (BST, UTC+1), the same 9:00 AM EST would be 3:00 PM in London — one hour later than during winter.

Example 2 — San Francisco to Mumbai A developer in San Francisco (PST, UTC-8) wants to schedule a 6:00 PM Friday call. In Mumbai (IST, UTC+5:30), that is 7:30 AM Saturday — across midnight and the date line. The 13-hour 30-minute gap catches many people off guard because IST uses a 30-minute offset rather than a whole hour.

Example 3 — Chicago to Sydney A 10:00 AM CST (UTC-6) Monday meeting in Chicago converts to 3:00 AM AEDT (UTC+11) Tuesday in Sydney during Australian summer. The 17-hour difference means Chicago morning calls land in the early hours in Sydney — making live overlap extremely limited without someone working outside normal hours.

Common Time Zone Reference Table

When to Use This Converter

• Scheduling video calls or meetings across offices in different countries
• Planning travel itineraries with arrival and departure times across zones
• Coordinating live events, webinars, or product launches for a global audience
• Checking whether a customer support window in one zone overlaps business hours in another
• Verifying deadlines — a 5:00 PM Friday deadline in New York is 10:00 PM Friday in London, not Monday

Common Mistakes

1. Forgetting DST transitions — the US and EU switch on different dates. Between mid-March and late-March, the US has already switched but Europe has not, shifting their typical gap by one hour for about two weeks.
2. Assuming all offsets are whole hours — India (UTC+5:30), Nepal (UTC+5:45), Iran (UTC+3:30), and parts of Australia (UTC+9:30) all use fractional offsets. A conversion that ignores the 30-minute component will be wrong by half an hour.
3. Crossing the date line without adjusting the day — converting from a Pacific zone to an East Asian zone often moves across midnight and changes the calendar date. Always check whether the converted time is the same day, the next day, or the previous day.
4. Using abbreviations that are not unique — CST means Central Standard Time (UTC-6) in the US, China Standard Time (UTC+8), and Cuba Standard Time (UTC-5). Always confirm what a three-letter abbreviation refers to when communicating internationally.

Context and Applications

Time zone conversion is foundational to international business. A multinational company with teams in New York, London, and Singapore deals with a 13-hour span from New York morning (9:00 AM EST) to Singapore end-of-day (10:00 PM SGT). The narrow overlap window — roughly 9:00 to 10:00 AM EST / 2:00 to 3:00 PM GMT / 9:00 to 10:00 PM SGT — is often the only time all three teams can meet live. Aviation, finance markets, and global logistics all rely on UTC as a single reference point to avoid exactly this kind of complexity.

Tips

• When sharing a meeting time internationally, always include the UTC offset in parentheses — “3:00 PM EST (UTC-5)” leaves no ambiguity
• Anchor recurring meetings to a fixed UTC time rather than a local time, so DST changes do not silently shift them
• Arizona (most of the state) does not observe DST and stays on MST (UTC-7) year-round — schedule accordingly when working with Phoenix teams
• For large global teams, choose a meeting time that falls within the 9-5 window for the majority of participants and rotate the inconvenient slot
• The International Date Line runs through the Pacific Ocean near UTC+12 — a Monday morning in Los Angeles can be Tuesday in Auckland at the same UTC moment
• World Clock Meeting Planner sites build on exactly this converter logic — knowing the math helps you sanity-check those tools when results look odd