Time Zone Converter

The time zone converter shows you the same instant in multiple cities at once. Pick a source city and a time, then add as many destinations as you need. Work-hour and likely-asleep badges help with meeting planning, and the entire thing runs in your browser using the IANA time zone database your operating system already has.

UTC (Coordinated Universal Time) is the global reference timeline. GMT (Greenwich Mean Time) is the older British name for essentially the same thing — they differ by less than a second and most people use them interchangeably. The letter Z (as in 2026-06-08T14:00Z) is the ISO 8601 way to write "UTC". It stands for Zulu time, from the NATO phonetic alphabet.

Every time zone is expressed as an offset from UTC. New York is UTC-5 in winter, UTC-4 in summer (DST). India is UTC+5:30 year round. Hawaii is UTC-10, no DST. When you store timestamps in a database, almost always store them in UTC and convert to local for display.

About 70 countries use daylight saving time, shifting clocks forward an hour in spring and back in fall. The exact dates differ by region, which is why "EST" is sometimes wrong — for half the year, US East Coast is actually EDT (UTC-4). The IANA zone database (America/New_York, etc.) handles the rules correctly. Avoid using bare offset names like "EST" in calendars and scheduling tools.

The 8/10/12 rule

For a meeting where everyone is in their work hours:

• Up to 8 hours apart (e.g., NYC to London): one of you takes early morning, the other afternoon
• 8-10 hours apart (e.g., NYC to Tokyo): one of you must take very early or very late, no overlap exists during normal work hours
• 12+ hours apart (NYC to Sydney): rotate who gets the bad time, or use async communication

Always include time zone in invites

"10am" means nothing across teams. "10am EDT" or "10am London" eliminates the most common scheduling error. The best calendar tools (Google Calendar, Outlook) handle this if you set your local zone correctly and let the tool convert.

Use the city, not the offset

"10am New York time" is clear in any season. "10am EST" is wrong for half the year (it would be EDT in summer). Pick a city in the destination zone.

What's the difference between EST and EDT?

EST (Eastern Standard Time) is UTC-5, used in winter. EDT (Eastern Daylight Time) is UTC-4, used in summer. Confusingly, most people say "EST" year-round even when they mean EDT. Avoid this in scheduling — use city names or full ISO timestamps.

Does China have multiple time zones?

Geographically, China spans 5 time zones, but officially the whole country uses Beijing time (UTC+8). This means dawn arrives at 10am in western China during winter. There's a strong unofficial Xinjiang Time (UTC+6) used locally.

What is Zulu time?

Zulu time = UTC. It's the military and aviation phonetic for the letter Z (used in ISO 8601 to denote UTC: 2026-06-08T14:00Z). Same as GMT in casual use, same as UTC for technical use.

How do I share a meeting time across zones?

Use a calendar tool with timezone support (Google Calendar, Outlook). Send the invite — recipients see it in their local zone. For plain text, write "10am EDT (NYC), 3pm BST (London), 7:30pm IST (Delhi)" or include a link to a tool like this one.

Which zones don't observe DST?

Most of Asia (China, Japan, India, all of Southeast Asia), Africa, much of South America, plus parts of the US (Arizona, Hawaii, most of Indiana before 2006). The list is shrinking — several countries have abolished DST recently (Russia in 2014, Mexico in 2022, Brazil in 2019).

What IANA zone should I use for "Indian time"?

Asia/Kolkata (formerly known as Asia/Calcutta — both still work). It's UTC+5:30 year round, no DST. Use this for any city in India, not "IST" — the abbreviation IST also stands for Irish Standard Time and Israeli Standard Time.