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Time Zone Calculator

Convert times between time zones. Enter a date and time, select source and target zones, and see the converted result instantly.

Time Zone Worksheet
: :
From: (UTC-5) Eastern Time (US/Canada)
11:03:00 AM
11:03:00
Sun, Oct 11, 2026
UTC-5
To: (UTC+9) Tokyo, Seoul
1:03:00 AM
01:03:00
Mon, Oct 12, 2026
UTC+9
Time Difference+14 hours
Day Change+1 day (next day)
From OffsetUTC-5
To OffsetUTC+9

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How Time Zones Work

The Earth is divided into time zones based on longitude. Each zone is defined as an offset from UTC (Coordinated Universal Time). Moving east adds hours; moving west subtracts them.

Conversion formula: Target Time = Source Time + (Target Offset - Source Offset)

Major Time Zones

AbbreviationNameUTC OffsetMajor Cities
HSTHawaii Standard-10Honolulu
PST/PDTPacific-8 / -7Los Angeles, Seattle
MST/MDTMountain-7 / -6Denver, Phoenix
CST/CDTCentral-6 / -5Chicago, Houston
EST/EDTEastern-5 / -4New York, Toronto
GMT/BSTGreenwich / British Summer+0 / +1London, Dublin
CET/CESTCentral European+1 / +2Paris, Berlin, Rome
ISTIndia Standard+5:30Mumbai, Delhi
CSTChina Standard+8Beijing, Shanghai
JSTJapan Standard+9Tokyo, Osaka
AEST/AEDTAustralian Eastern+10 / +11Sydney, Melbourne
NZST/NZDTNew Zealand+12 / +13Auckland, Wellington

Daylight Saving Time (DST)

Many regions shift clocks forward by 1 hour in spring and back in fall. During DST, the effective offset changes:

  • US Eastern: EST (UTC-5) → EDT (UTC-4) from March to November
  • UK: GMT (UTC+0) → BST (UTC+1) from March to October
  • No DST: Hawaii, Arizona, Japan, China, India, and most equatorial countries

Quick Reference: Time Differences from UTC

When it's noon (12:00) UTC...Local Time
Los Angeles (PST)4:00 AM
New York (EST)7:00 AM
London (GMT)12:00 PM
Dubai (GST)4:00 PM
Mumbai (IST)5:30 PM
Tokyo (JST)9:00 PM
Sydney (AEST)10:00 PM

Tips for Working Across Time Zones

  • Schedule in UTC: When coordinating across zones, agreeing on UTC avoids confusion
  • Use 24-hour format: Eliminates AM/PM ambiguity across cultures
  • Note the date: Large offsets can shift the date — 10 PM Monday in New York is 12 PM Tuesday in Tokyo
  • Account for DST: Check whether DST is active in both locations at the time of your event
  • International Date Line: Crossing UTC+12/UTC-12 changes the calendar date by one day

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Frequently Asked Questions

What time is it in London when it is 9 AM in New York?

It is 2 PM in London, because New York (EST, UTC-5) is 5 hours behind London (GMT, UTC+0). A 9 AM to 5 PM New York workday equals 2 PM to 10 PM in London, so the shared business-hours overlap is roughly 9 AM to 12 PM New York time. The gap shrinks to 4 hours for a few weeks a year when the two switch daylight saving time on different dates.

What is UTC?

UTC, Coordinated Universal Time, is the global time standard that every time zone is defined against. Eastern Time is UTC-5 and Tokyo is UTC+9, so Tokyo is 14 hours ahead of Eastern Time. UTC never shifts for daylight saving time, which makes it the safe reference for scheduling across countries.

What is the difference between EST and EDT?

EST, Eastern Standard Time, is UTC-5 and applies in winter. EDT, Eastern Daylight Time, is UTC-4 and applies during daylight saving time from spring to autumn. A conversion that uses the wrong one lands an hour off, so use the offset in effect on the date being converted.

How many time zones are there?

There are 38 distinct UTC offsets in use, ranging from UTC-12 (Baker Island) to UTC+14 (Line Islands). Several are not whole hours: India uses UTC+5:30, Nepal UTC+5:45, Iran UTC+3:30 and Newfoundland UTC-3:30. Because the offsets run from -12 to +14 either side of the International Date Line, two places can be 26 hours apart.