About Timezone Prime

A free time zone converter built to give the right answer on any date, not just today.

Timezone Prime converts a time from one zone to another and shows both clocks over a ribbon of the day, so you can see at a glance whose working hours overlap. It started as a tool for scheduling calls across India, Europe and North America, where daylight saving shifts the difference twice a year and catches people out.

How the conversions work

Every calculation uses the IANA time zone database, the same rules your phone and computer use. The database is built into your browser, so conversions run on your device and follow each region's daylight saving dates for the exact day you pick, including past and future years.

Abbreviations such as EST, IST or CET are labels for people. Behind each one is a specific IANA zone, for example America/New_York or Asia/Kolkata, and that zone decides the offset.

What you will find here

A converter for any pair of zones, with a date picker and a 12 or 24 hour clock.
100 dedicated pages for common conversions, each with an hour-by-hour table.
A world map that highlights both zones and every place sharing their offset.
An FAQ covering time differences, daylight saving and meeting times.

Data and credits

Time zone rules come from the IANA tz database through your browser. Map boundaries come from Timezone Boundary Builder, published under the Open Database License.

Privacy by design

There are no accounts, no ads and no tracking. Your theme and clock format are remembered in your own browser and never sent to us. The privacy policy has the details.

Get in touch

Spotted a wrong offset or want a conversion page added? We read every message.