Julian Date Converter
Gregorian to Julian Day Number
Convert a Gregorian calendar date to a Julian Day Number
Julian Day Number to Gregorian
Convert a Julian Day Number back to a Gregorian date
Formula
JDN = d + floor((153m+2)/5) + 365y + floor(y/4) - floor(y/100) + floor(y/400) - 32045
Frequently Asked Questions
What is a Julian Day Number?
The Julian Day Number (JDN) is a continuous count of days since the beginning of the Julian Period on January 1, 4713 BC (proleptic Julian calendar). It is used in astronomy, chronology, and historical dating.
What is the Modified Julian Date?
The Modified Julian Date (MJD) equals JDN minus 2400000.5. It was introduced to use smaller numbers and to start the day at midnight rather than noon. MJD 0 is November 17, 1858.
Is this the same as the Julian Calendar?
No. The Julian Day Number is a continuous day count used in astronomy. The Julian Calendar is the calendar system introduced by Julius Caesar in 46 BC, predecessor to the Gregorian calendar.
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