Astronomy Answers: From the Astronomical Dictionary

Astronomy Answers
From the Astronomical Dictionary

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The description of the word you requested from the astronomical dictionary is given below.

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.