Astronomy Answers: From the Astronomical Dictionary

Astronomy Answers
From the Astronomical Dictionary


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the Julian Day Number

The Julian Day Number (JDN) counts the number of whole days since 12:00 UTC or 12:00 TAI on January 1st, −4712 on the Julian proleptic calendar. You get the Julian Day Number if you round a Julian Date (JD) down to the nearest whole value.