Time Zone Converter -- Between Cities & Zones

Convert Time Between Zones

How Time Zone Conversion Works

A time zone converter is a tool that translates a specific time in one time zone to the equivalent time in another. It works by comparing each zone's offset from Coordinated Universal Time (UTC), the global time standard.

The Conversion Formula

Time zone conversion follows a simple formula:

1. Find the UTC offset for each time zone on the specific date (offsets change during Daylight Saving Time).
2. Calculate the difference: Target offset − Source offset = Hours to add or subtract.
3. Apply the difference to the source time. If the result goes past midnight, adjust the date.

Worked Example: New York to Tokyo

Convert 3:00 PM Eastern Time (EST, UTC−5) to Japan Standard Time (JST, UTC+9):

• Difference: UTC+9 − UTC−5 = 14 hours ahead
• 3:00 PM + 14 hours = 5:00 AM the next day in Tokyo

Worked Example: London to Los Angeles

Convert 10:00 AM GMT (UTC+0) to Pacific Time (PST, UTC−8):

• Difference: UTC−8 − UTC+0 = 8 hours behind
• 10:00 AM − 8 hours = 2:00 AM the same day in Los Angeles

What Is UTC?

UTC (Coordinated Universal Time) is the primary time standard by which the world regulates clocks. Every time zone is defined as an offset from UTC. UTC does not observe Daylight Saving Time, making it a stable reference point for international coordination. It replaced GMT as the formal standard, though the two are functionally identical at UTC+0.

Daylight Saving Time (DST)

DST shifts clocks forward by 1 hour in spring and back in fall in participating regions. This changes the UTC offset — for example, US Eastern Time is UTC−5 in winter (EST) but UTC−4 in summer (EDT). Not all regions observe DST: Japan, China, India, most of Africa, and Arizona (US) do not. This tool applies DST rules automatically for the selected date using the IANA time zone database.

Half-Hour and 45-Minute Offsets

Not all time zones use whole-hour offsets. India (UTC+5:30), Nepal (UTC+5:45), Iran (UTC+3:30), and parts of Australia (UTC+9:30) use fractional offsets. These exist because countries chose an offset that best aligned with their geographic solar noon rather than rounding to the nearest hour.

Common Time Zone Differences

Quick reference for frequently converted time zone pairs. Differences shown are standard time; DST may shift by ±1 hour during transition weeks.

Differences are for standard time (non-DST). During DST transition weeks, some pairs shift by 1 hour because regions change clocks on different dates.

Popular Time Zones

Common Mistakes When Converting Time Zones

• Using a static offset year-round. UTC offsets change during DST transitions. London is UTC+0 in winter but UTC+1 in summer. Always check the offset for the specific date you're converting.
• Forgetting date changes. A 14-hour time difference means afternoon in one city is early morning the next day in another. Always check whether the date changes when the conversion crosses midnight.
• Assuming DST transitions happen on the same date everywhere. The US, EU, and Australia switch to/from DST on different weekends. This means the time difference between two cities can temporarily shift by 1 hour during transition weeks (typically March/April and October/November).
• Confusing timezone abbreviations. "CST" can mean US Central Standard Time (UTC−6), China Standard Time (UTC+8), or Cuba Standard Time (UTC−5). Use IANA timezone names (e.g., "America/Chicago") or explicit UTC offsets to avoid ambiguity.
• Ignoring half-hour offsets. India (UTC+5:30), Iran (UTC+3:30), and Nepal (UTC+5:45) do not use whole-hour offsets. Converting "5 hours ahead" to India is incorrect — it's 5 hours and 30 minutes.
• Converting from the wrong reference. "EST" always means UTC−5. If you're in Eastern Time during summer, you're in EDT (UTC−4), not EST. Mixing these up shifts your conversion by 1 hour.

Frequently Asked Questions

How do I convert time between time zones?

Find the UTC offset for each zone and calculate the difference. For example, New York (UTC−5) to London (UTC+0) is a 5-hour difference — add 5 hours to New York time to get London time. This tool does this automatically, including Daylight Saving Time adjustments for the specific date you select.

What is UTC and how does it relate to time zones?

UTC (Coordinated Universal Time) is the global time standard. Every time zone is defined as a fixed offset from UTC — for example, EST is UTC−5 and JST is UTC+9. UTC does not observe Daylight Saving Time, which makes it a stable reference for international coordination.

What is the difference between GMT and UTC?

GMT (Greenwich Mean Time) and UTC are often used interchangeably because they share the same offset (UTC+0). However, UTC is a precise atomic time standard maintained by international laboratories, while GMT was historically based on solar observations. For everyday use, they are identical.

How does Daylight Saving Time affect time zone conversion?

DST shifts clocks forward by 1 hour in spring and back in fall, changing the UTC offset for affected zones. For example, US Eastern Time is UTC−5 in winter (EST) but UTC−4 in summer (EDT). Not all regions observe DST — Japan, China, India, and Arizona (US) do not. Always use the offset for the specific date you're converting.

What time zones use half-hour or 45-minute offsets?

India Standard Time is UTC+5:30. Nepal Time is UTC+5:45. Iran Standard Time is UTC+3:30. Australia's Northern Territory and South Australia use UTC+9:30. Afghanistan is UTC+4:30. The Chatham Islands (New Zealand) use UTC+12:45. These fractional offsets exist because countries aligned their clock time with local solar noon.

What is the International Date Line?

The International Date Line runs roughly along the 180° meridian in the Pacific Ocean. Crossing it westward adds a day; crossing eastward subtracts a day. This is why nearby islands like Samoa (UTC+13) and American Samoa (UTC−11) can be a full day apart on the calendar.

Why do some countries have multiple time zones?

Countries that span a wide east-west distance use multiple time zones to keep clock time aligned with solar time. The US has 6 zones, Russia has 11, and Australia has 3. China is the notable exception — despite spanning 5 geographic zones, it uses a single time zone (UTC+8) for political unity.

What is the time difference between New York and London?

London is typically 5 hours ahead of New York. When it's noon in New York, it's 5:00 PM in London. This changes to 4 hours for a few weeks in spring and fall because the US and UK switch DST on different dates.

Does this tool account for Daylight Saving Time?

Yes. The tool uses the Intl.DateTimeFormat API, which includes the full IANA time zone database with historical and current DST rules. It automatically applies the correct offset for the specific date and time zone you select.

How do I convert UTC to my local time?

Select "UTC" as the "From" timezone and your local city as the "To" timezone, then enter the UTC time. The tool converts it to your local time with DST applied. Alternatively, simply add your local UTC offset to the UTC time — for example, UTC+2 means adding 2 hours to UTC.

Does this tool store my data?

No. All conversions happen in your browser using JavaScript and the built-in Intl API. No data is sent to any server. The tool works offline after the page loads.

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• Time Zones Explained — UTC, GMT, Offsets, and DST — how time zones work and how to convert between them
• How to Schedule Meetings Across Time Zones — practical guide for remote team scheduling

Privacy & Limitations

• Client-side only. No data is sent to any server. All conversions use your browser's built-in Intl API and the IANA time zone database. No cookies, no tracking.
• DST is handled automatically. The tool applies correct DST rules for the selected date using the IANA database bundled in your browser. Very old dates or recently changed DST rules may vary by browser version.
• 40+ cities supported. The most commonly needed time zones are included. For less common zones, use the IANA timezone name (e.g., "Pacific/Fiji") — the tool may not list every zone in the dropdown.
• Accuracy depends on your browser. The Intl API relies on the time zone data shipped with your browser and operating system. Keep both updated for the most accurate results.

Time Zone Converter FAQ