Julian Date Converter

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Convert calendar dates to Julian Day Numbers (JDN), Modified Julian Dates (MJD), and Julian calendar dates, and vice versa.

Convert Gregorian Date

Julian Day (JD): —

Modified Julian (MJD): —

Convert Julian Day (JDN)

Gregorian Date: —

Day of the Week: —

Gregorian Calendar and Julian Day Conversions

The Julian Day Number (JDN) is a continuous count of days starting from January 1, 4713 BC. This system is heavily utilized by astronomers, software developers, and historical researchers to compute time difference intervals without dealing with complicated monthly calendar systems.

Use our dual converter to instantly switch values between the Gregorian calendar and JDN/MJD formats.

Frequently Asked Questions

MJD is defined as JD - 2400000.5, shifting the start of the day from noon to midnight, and shortening the numbers for modern databases.

A standard Julian Day begins at 12:00 UTC (noon), whereas Gregorian calendar days start at midnight.