Time Zone Converter

Convert times across global time zones, calculate exact hour differences, and coordinate international meetings without scheduling errors.

Time Zone Selection

Popular City Routes

Select time zones on the left

Pick date, time, and origin/destination cities to compute the global time difference.

Time Zone Mathematics & UTC Offset Calculations

The Earth rotates 360° on its axis every 24 hours, meaning the solar day advances 15° of longitude per hour (1° every 4 minutes). Coordinated Universal Time (UTC) serves as the primary reference meridian (0° longitude at the Royal Observatory in Greenwich, London).

1. Universal Time Zone Conversion Formula
Target Local Time=Source Local Time+(Target UTC Offset − Source UTC Offset)
2. Longitudinal Solar Time Equation
Solar Time Delta (Hours)=
Δ Longitude (Degrees)15° / Hour
Step-by-Step Calculation Breakdown
Step 1: Determine UTC Offsets (New York EST to London GMT)
Source Timezone (New York): UTC−5
Target Timezone (London): UTC+0
Step 2: Calculate Hour Delta
Hour Difference = 0 − (−5) = +5 Hours Ahead
Step 3: Apply Shift to 2:30 PM (14:30)
London Time=14:30 + 5 Hours=19:30 (7:30 PM Same Day)

Major Global Time Zones Reference Table

Region & CitiesAbbrStandard UTCDST Observation
US Pacific (LA, SF, Seattle)PST / PDTUTC−8Yes (Mar – Nov: UTC−7)
US Eastern (NY, Miami, Boston)EST / EDTUTC−5Yes (Mar – Nov: UTC−4)
Western Europe (London, Dublin)GMT / BSTUTC+0Yes (Mar – Oct: UTC+1)
Central Europe (Paris, Berlin, Rome)CET / CESTUTC+1Yes (Mar – Oct: UTC+2)
Japan & Korea (Tokyo, Seoul)JST / KSTUTC+9No DST observed
East Australia (Sydney, Melbourne)AEST / AEDTUTC+10Yes (Oct – Apr: UTC+11)

Frequently Asked Questions

How many time zones are there worldwide?
The world is divided into 24 primary nautical time zones, each approximately 15° of longitude wide. However, with half-hour and quarter-hour regional offsets (such as India UTC+5:30 and Nepal UTC+5:45), there are approximately 38 active civil time offsets worldwide.
What does UTC stand for?
UTC stands for Coordinated Universal Time (Temps Universel Coordonné). It is the high-precision atomic time standard that replaced Greenwich Mean Time (GMT) for international civil and scientific timekeeping.
How does Daylight Saving Time (DST) affect conversions?
Daylight Saving Time advances clocks forward by 1 hour during spring and summer months. Because different countries transition to DST on different calendar dates (and many equatorial countries do not observe DST at all), time differences between cities can shift temporarily throughout the year.
How do I schedule an international meeting across multiple time zones?
Use UTC as a common anchor or find the overlapping business hours (typically 9:00 AM to 5:00 PM local time). For example, between New York (UTC-5) and London (UTC+0), a 9:00 AM New York meeting occurs at 2:00 PM in London.

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