World Time Zone Calculator
Live calculator

World Time Zone Calculator & Converter

Instant, real-time world clock and time zone difference calculator. Compare 500+ cities with DST auto-detection and business hours overlap. Free.

Time zone calculator online Live and date-aware
Previewing now
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New York
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London
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Tokyo
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Time zone calculator by city, by location, and with date.
Quick conversions

Popular zone conversions

Open a saved comparison in the time zone calculator tool.

By city pair

World City Time Differences Directory

Instantly compare time differences between major cities worldwide. Use our live city-to-city converters to schedule meetings and travel across borders.

See all city pair calculators →
Directory

World Time Zones by Country and City

Browse our comprehensive directory of time zones by country and city. Check current local time, UTC offsets, and daylight saving rules for any location.

See all locations →
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Interactive Guide

Convert Any Time, Anywhere

A comprehensive guide to time zone conversions, UTC, and Daylight Saving Time.

Our time zone calculator converts a time from one location to its equivalent in another, seamlessly accounting for the UTC offset and daylight saving time (DST) of both places. Enter a date, a time, and your two locations, and you'll instantly get the exact converted result — no manual math, and no guessing whether a region has switched its clocks.

The Math Behind the Conversion

Two cities can be "5 hours apart" in January and only "4 hours apart" in July because of daylight saving. A reliable calculator handles this automatically.

Step 1: Source
3:00 PM
New York (ET)
→
+4 hrs
Step 2: Universal
7:00 PM
UTC Base Time
→
+9 hrs
Step 3: Target
4:00 AM
Tokyo (JST)
Next Day
FAQ

Frequently asked questions

What is a time zone calculator?
A time zone calculator is a tool that converts the current time between different time zones, helping you schedule meetings, calls, and events across cities and countries.
How do I calculate time zone differences?
Use the calculator above: add two or more cities, and the tool shows you the real-time offset and current local time for each location, including daylight saving adjustments.
Does the calculator account for daylight saving time?
Yes. World Time Zone Calculator uses IANA time zone data through your browser's Intl API, which automatically adjusts for DST changes in every supported region.
Can I compare more than two time zones?
Absolutely. Add as many cities as you need using the input field, and all times update together when you scrub the time slider or change the date.
Is there a mobile app version?
World Time Zone Calculator is a progressive web app — add it to your home screen from any mobile browser for an app-like experience with no download required.
How do I convert time zones accurately?
Convert the source time to UTC first, then apply the target zone's current offset — including daylight saving if it's in effect on that date. A converter automates this step so you don't track DST rules manually.
What's the actual difference between GMT and UTC?
GMT is a specific time zone observed in the UK during winter. UTC is the global time standard that never shifts for daylight saving. They align for part of the year but aren't identical.
Why do some countries use 30- or 45-minute offsets?
Those offsets are national decisions, not geographic requirements. India (UTC+5:30) and Nepal (UTC+5:45) both chose non-hourly offsets rather than aligning to the nearest full hour.