Time Zone Converter
Convert between world time zones
How Time Zones Work
The world is divided into 24 primary time zones, each roughly 15 degrees of longitude wide, measured as offsets from Coordinated Universal Time (UTC). When you travel east, clocks move forward; when you travel west, clocks move backward. Some regions use half-hour or quarter-hour offsets, such as India (UTC+5:30) and Nepal (UTC+5:45).
Major World Time Zones
The most commonly referenced time zones include Eastern Standard Time (EST, UTC-5) used in New York, Central Standard Time (CST, UTC-6) used in Chicago, Pacific Standard Time (PST, UTC-8) used in Los Angeles, Greenwich Mean Time (GMT, UTC+0) used in London, Central European Time (CET, UTC+1) used in Paris and Berlin, India Standard Time (IST, UTC+5:30) used across India, and Japan Standard Time (JST, UTC+9) used in Tokyo.
Daylight Saving Time
Many countries observe Daylight Saving Time (DST), shifting clocks forward by one hour during warmer months. In the United States, DST runs from the second Sunday in March to the first Sunday in November. Not all countries observe DST, and some countries that previously used it have discontinued the practice. When scheduling international meetings, always verify whether DST is currently in effect in each relevant time zone.
Scheduling Across Time Zones
When scheduling meetings across multiple time zones, aim for overlapping business hours. For example, the overlap between New York (EST) and London (GMT) business hours is typically 9 AM to 12 PM EST (2 PM to 5 PM GMT). For teams spanning the US and Asia, early morning US time or late evening Asian time often works best. Using this converter helps find the optimal meeting time for all participants.
Planning tips
Date and time calculations are useful for planning deadlines, birthdays, trips, work schedules, and reminders. Always check the start date, end date, and time zone before relying on the result. For travel or international work, daylight saving time and local calendar rules can affect the final answer. Use the calculator as a quick planning tool, then confirm critical dates in your calendar.
Time Zone Converter: practical guide
The Time Zone Converter is built for people who want a fast answer without losing context. It keeps the calculation simple, shows the result clearly, and helps you understand what the number means before you use it in a real decision.
Date and time calculations are useful for planning deadlines, schedules, durations, and milestones. Calendar rules can be less obvious than they look, especially across months, leap years, and time zones.
What is the best way to use the Time Zone Converter?
Enter the values carefully, review the units, and use the result as a reliable reference point. The Time Zone Converter is most useful when you compare scenarios or repeat the calculation with consistent inputs.
Is the Time Zone Converter accurate?
The calculator follows standard calculation logic, but accuracy depends on the values you enter and the assumptions behind the formula. For important date & time decisions, use it as guidance and verify the result with a trusted source.
Understanding time zones
Time zones are regions of the Earth that observe a uniform standard time for legal, commercial, and social purposes. The world is divided into 24 standard time zones, each roughly corresponding to 15 degrees of longitude (since the Earth rotates 360° in 24 hours, covering 15° per hour). In practice, time zone boundaries follow political and geographical lines rather than strict meridians, creating irregular shapes and some unusual offsets (like the 5:30 or Nepal's 5:45 offset from UTC).
Understanding UTC — the global time standard
UTC (Coordinated Universal Time) is the basis for all time zones worldwide. Every time zone is expressed as UTC plus or minus an offset. UTC never changes for daylight saving — it is the fixed reference point. New York is UTC–5 (EST) or UTC–4 (EDT in summer). London is UTC+0 (GMT) or UTC+1 (BST in summer). Tokyo is UTC+9 year-round. Sydney is UTC+10 (AEST) or UTC+11 (AEDT in summer). Dubai is UTC+4 year-round.
Common time zone conversions from IST
- IST → UTC (Greenwich Mean Time): Subtract 5 hours 30 minutes. 12:00 IST = 06:30 UTC
- IST → EST (New York, US Eastern Standard): Subtract 10 hours 30 minutes. 12:00 IST = 01:30 EST (previous day). During EDT (summer): subtract 9 hours 30 minutes.
- IST → PST (Los Angeles, US Pacific Standard): Subtract 13 hours 30 minutes. 12:00 IST = 22:30 PST (previous day). During PDT: subtract 12 hours 30 minutes.
- IST → GMT/BST (London): GMT: subtract 5 hours 30 min. BST (British Summer Time, March–October): subtract 4 hours 30 min.
- IST → CET (Paris, Berlin): Subtract 4 hours 30 min (standard). Subtract 3 hours 30 min (Central European Summer Time, March–October).
- IST → SGT (Singapore): Add 2 hours 30 minutes. 12:00 IST = 14:30 SGT. Singapore also has no DST.
- IST → JST (Tokyo): Add 3 hours 30 minutes. 12:00 IST = 15:30 JST.
- IST → AEST (Sydney, Australian Eastern Standard): Add 4 hours 30 min (AEST) or 5 hours 30 min (AEDT summer).
- IST → Dubai (UAE): Subtract 1 hour 30 minutes. 12:00 IST = 10:30 UAE. UAE has no DST.
Daylight Saving Time — what it is and which countries use it
Daylight Saving Time (DST) moves the clock forward by 1 hour in summer to extend evening daylight. Typically, clocks "spring forward" in March/April and "fall back" in October/November. Countries that observe DST include the US, Canada, most of Europe, and Australia. Countries that do NOT observe DST include India, China, Japan, UAE, Singapore, and most of Asia and Africa.
DST creates complications for international scheduling: the time difference between India and the US changes twice per year. A meeting scheduled at "10 AM IST, 12:30 AM EST" in January becomes "10 AM IST, 12:30 AM EDT" in summer — but EDT is UTC–4, not UTC–5, so the US equivalent time actually becomes 11:30 PM EST the previous evening when the US switches to DST. Always verify DST status when scheduling international meetings, especially near the transition dates.
Best practices for scheduling international meetings
- Use UTC as the reference: Express the meeting time in UTC alongside local times. UTC never changes.
- Specify the date and both time zones explicitly: "Monday 15 June, 10:00 IST (04:30 UTC)" is unambiguous. "Monday 10 AM" is not.
- Account for DST in advance: Check whether the other party's country is on standard time or DST at the specific meeting date
- Use meeting scheduling tools: Calendly, World Time Buddy, and Google Calendar with time zone support handle the conversions automatically
- For recurring meetings: Note whether the meeting time is fixed to a specific UTC time (and will shift in local time when DST changes) or fixed to a local time (and the UTC equivalent will shift)
Frequently asked questions
Why does India have a 30-minute offset (UTC+5:30)? the 5.5-hour offset reflects a compromise when the country standardised its time zone at independence. The geographic centre of India falls between the UTC+5 and UTC+6 lines, and the half-hour offset provides a reasonable average. Several countries use non-standard offsets: Nepal (UTC+5:45), Iran (UTC+3:30), Australia's Northern Territory (UTC+9:30).
What is UTC and how is it different from GMT? UTC (Coordinated Universal Time) is the primary time standard by which the world regulates clocks. GMT (Greenwich Mean Time) is a time zone at 0° longitude. For practical purposes, UTC and GMT are equivalent. UTC is the technical standard used in computing and international coordination; GMT is the historical designation for the same reference time.
How do I convert a Unix timestamp to a human-readable date? The Unix timestamp counts seconds since 1 January 1970 UTC. Divide by 86,400 (seconds per day) to get days since epoch, then add to 1 January 1970. In JavaScript: new Date(timestamp × 1000). In Python: datetime.fromtimestamp(timestamp). Most date/time calculators handle this conversion directly.