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Time & Date tool

Time Zone Converter

Convert one local date and clock time between time zones, with the UTC instant and offsets shown clearly.

Free · Private · Runs in your browser

Civil-time conversion

Convert one local time

Enter a date, clock time, and two IANA time zones. The converter uses the timezone rules installed in your browser.

Use full IANA names such as America/New_York or Asia/Kathmandu. Short labels such as EST and CST are intentionally unsupported because they can mean different places.

The converted date, time, UTC offset, and exact instant will appear here.

How the conversion works

Aletheia resolves the entered civil time against its IANA time zone, identifies the matching UTC instant, and displays that same instant in the destination zone. Offsets are calculated for the selected date rather than treated as permanent.

Daylight-saving transitions

When a clock moves forward, some local times never occur. When a clock moves back, some local times occur twice. The converter refuses nonexistent times and asks you to choose the earlier or later occurrence when a time is repeated.

Boundaries

This tool supports civil dates from 1970 through 2100 using the timezone rules installed in the current browser. Government rule changes may require a browser or operating-system update. The tool is not intended to establish historically authoritative local time or calculate legal deadlines.

Related tools

Use the Time Calculator for fixed durations or the Date Duration Calculator for calendar-day differences.

Version

Calculation version 1.0.0. Inputs and results remain in the browser and are not included in analytics.

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