Time Zone Calculator

Convert time between different time zones instantly.

About This Calculator

Coordinate across the globe with the Time Zone Calculator. In our interconnected world, managing time differences is essential for business calls, virtual meetings, and staying connected with friends and family across continents. This tool eliminates the mental math and confusion of international scheduling.

The world is divided into 24 primary time zones, each roughly 15 degrees of longitude wide, though political boundaries often create irregular zone shapes. The baseline is Coordinated Universal Time (UTC), formerly known as Greenwich Mean Time (GMT). Understanding time zones isn't just about adding or subtracting hours—it's about knowing when tomorrow starts in Tokyo while it's still today in New York, and navigating the International Date Line.

Daylight Saving Time (DST) adds another layer of complexity. Not all countries observe DST, and those that do may switch on different dates. For example, the time difference between New York and London varies from 4 to 6 hours throughout the year depending on when each region changes clocks. Our calculator handles these complexities automatically.

Time Zone Offset Formula

Target Time = Source Time + (Target UTC Offset - Source UTC Offset)

Example: 3:00 PM EST (UTC-5) → Tokyo JST (UTC+9): 3:00 PM + (9 - (-5)) = 3:00 PM + 14 = 5:00 AM (next day)

Major Time Zones Reference

Time Zone	UTC Offset	Major Cities
PST/PDT	UTC-8/-7	Los Angeles, Seattle, Vancouver
EST/EDT	UTC-5/-4	New York, Toronto, Miami
GMT/BST	UTC+0/+1	London, Dublin, Lisbon
CET/CEST	UTC+1/+2	Paris, Berlin, Rome
IST	UTC+5:30	Mumbai, Delhi, Bangalore
CST (China)	UTC+8	Beijing, Shanghai, Hong Kong
JST	UTC+9	Tokyo, Osaka, Seoul

Practical Examples

Business call: 9:00 AM in New York = 2:00 PM in London = 11:00 PM in Tokyo
Global standup: 5:00 PM London works for SF (9 AM), NYC (12 PM), and Singapore (1 AM next day)
Date line crossing: Flying from Tokyo to LA on Monday, you may arrive on Monday morning!

Pro Tips for Global Scheduling

Use "overlap hours" (usually 8-11 AM local) for meetings spanning many time zones
Always specify the time zone when scheduling (e.g., "3 PM ET" not just "3 PM")
Remember DST transitions happen on different dates in different countries
Some zones are 30 or 45 minutes offset (India, Nepal, parts of Australia)

Scenario Comparison

Scenario	Source Time	Target Zone	Converted Time
US-Europe business call	9:00 AM EST	CET (Paris)	3:00 PM CET
US-Asia meeting	6:00 PM PST	JST (Tokyo)	11:00 AM JST (+1 day)
UK-Australia call	2:00 PM GMT	AEDT (Sydney)	1:00 AM AEDT (+1 day)
India-US collaboration	10:00 PM IST	EST (New York)	11:30 AM EST

Common Mistakes to Avoid

Ignoring Daylight Saving Time: US and Europe switch DST on different dates. The time difference varies 4-6 hours throughout the year.
Forgetting date line crossings: When converting across the International Date Line, you may gain or lose a calendar day. Always verify the date.
Assuming whole-hour offsets: India is UTC+5:30, Nepal is UTC+5:45. Don't round—those 30-45 minutes matter for scheduling.
Not specifying AM/PM or 24-hour time: "3 o'clock" is ambiguous. Always clarify 3:00 AM vs 3:00 PM or use 15:00 format.

Reference Standards

Time Zone	UTC Offset	Major Cities
PST/PDT	UTC-8 / UTC-7	Los Angeles, Seattle, Vancouver
EST/EDT	UTC-5 / UTC-4	New York, Toronto, Miami
GMT/BST	UTC+0 / UTC+1	London, Dublin, Lisbon
JST	UTC+9	Tokyo, Seoul, Osaka

When to Use This vs Others

This calculator: Best for scheduling international meetings, flight planning, and coordinating across time zones.
Age Calculator: Use for calculating duration between dates, not time zone conversions.
Unit Converter: Use for measurement conversions (length, weight, temperature), not time.
Percentage Calculator: Use for calculating percentages and ratios in financial or math contexts.

Related tools: Age Calculator for date calculations, Unit Converter for other conversions, and Percentage Calculator for quick math.