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Julian Date Converter

Time & Date · Free Online Tool

Convert between Gregorian date and Julian Day Number (JDN).

By EZ4Code TeamLast updated: 2026-10-29

Date → JDN

JDN → Date

Both Directions

Convert Gregorian → JDN and JDN → Gregorian.

Algorithmic

Uses the standard integer JDN algorithm, no lookup tables.

Copyable

Copy the JDN with one click for use elsewhere.

How to Use Julian Date Converter

1Enter the time, date, or value you want to convert.
2Select the target format or timezone.
3The tool calculates the result instantly.
4Copy the converted value for your use.

Features

✓100% free — no signup, no subscription, no ads
✓Runs entirely in your browser — data never leaves your device
✓Fast and lightweight — instant results
✓Cross-platform — works on desktop, tablet, and mobile

Frequently Asked Questions

What timezone is used by default?

The Timestamp Converter uses UTC by default but can display results in your local timezone.

Can I convert timestamps from different programming languages?

Yes, the tool supports Unix timestamps (seconds and milliseconds), ISO 8601, and various date string formats.

Does daylight saving time affect the result?

Timezone conversions apply the daylight saving rules of the selected region. If you need a fixed offset, pick a UTC offset zone instead of a named city.

What is the difference between Unix seconds and milliseconds?

Seconds-based Unix time has 10 digits (typical for servers and databases); milliseconds has 13 digits (typical for JavaScript Date). The converter auto-detects the unit and lets you override it.