## Julian day |

**Julian day** is the continuous count of days since the beginning of the Julian Period and is used primarily by ^{[1]}

The Julian Day Number (JDN) is the integer assigned to a whole solar day in the Julian day count starting from noon ^{[2]}^{[3]}^{[4]} a date at which three multi-year cycles started (which are: ^{[5]} For example, the Julian day number for the day starting at 12:00 ^{[6]}

The Julian date (JD) of any instant is the Julian day number plus the fraction of a day since the preceding noon in Universal Time. Julian dates are expressed as a Julian day number with a decimal fraction added.^{[7]} For example, the Julian Date for 00:30:00.0 UT January 1, 2013, is 2 456 293.520 833.^{[8]} Expressed as a Julian date, right now it is 2458874.5104167. [ ]

The Julian Period is a ^{[9]} The Julian calendar year 2020 is year 6733 of the current Julian Period. The next Julian Period begins in the year AD 3268. Historians used the period to identify Julian calendar years within which an event occurred when no such year was given in the historical record, or when the year given by previous historians was incorrect.^{[10]}

- terminology
- variants
- history
- julian day number calculation
- julian date calculation
- see also
- notes
- references

The term *Julian date* may also refer, outside of astronomy, to the day-of-year number (more properly, the ^{[11]} or it may refer to dates in the *"Julian calendars"*,^{[11]} but this could also mean that the calendars are of years in the Julian calendar system.

Historically, Julian dates were recorded relative to ^{[12]} Seidelmann indicates that Julian dates may be used with ^{[13]} The fraction of the day is found by converting the number of hours, minutes, and seconds after noon into the equivalent decimal fraction. Time intervals calculated from differences of Julian Dates specified in non-uniform time scales, such as UTC, may need to be corrected for changes in time scales (e.g. ^{[7]}