JULIAN DATE
Return to STARS
The Julian Date (JD), or Julian Day Number, is a running count of days that starts at noon on January 1, 4713 BCE of the Julian Calendar. The date changes at noon, Greenwich (Universal) Time.
The Julian Date method of indicating a particular date is as follows:
yyyyddd yyyy = year ddd = day This method of datekeeping is used extensively by the US Military, although sometimes in a modified format (yddd).
Julian Date
(a) JD: The number of ephemeris days that have elapsed since 12h ephemeris time on January 1, 4713 B.C. JD for 1970 January 1 is 2440588.
(b) The interval of time in days and fraction of a day since 4713 B.C.
Julian date The number of days since noon on 1st January 4713 B.C. It is useful for astronomical observations as it saves confusion with other calendars.
Julian date (JD). The interval of time in days (and fraction of a day) since Greenwich noon on Jan. 1, 4713 BC.
The Julian date is the interval of time in days and fractions of a day, since January 1, 4713 BC Greenwich noon, Julian proleptic calendar. In precise work, the timescale, e.g., Terrestrial Time or Universal Time , should be specified....
B = 1900.0 + (Julian date âˆ' 2415020.31352) / 365.242198781
The standard epoch that was in use before the current standard epoch (J2000.0) was B1950.0, a Besselian epoch.
If you're looking for a way to challenge advanced students, have them express their data in terms of "Julian date, ...
After One, subsequent Julian dates are sequential. Therefore, before January 1, 1982 is Julian Date 2,444,970.5. The system, defined as the Julian date minus 2,400,000.5, is also occasionally used by astronomers, but not so frequently in recent years.
On Earth, astronomers often prefer to use Julian dates for timekeeping purposes. This is simply a sequential count of days, bypassing the complications of calendars.
In precise work the timescale, e.g., dynamical time or Universal Time, should be specified. [S92]
Julian Date, Modified
MJD -- The Julian Date minus 2400000.5. [S92]
Julian Proleptic Calendar ...
It includes routines for conversions between Universal Time (UTC), Atomic Time (TAI), and Ephemeris Time (ET). It also performs conversions between calendar dates and Julian dates, and interprets or formats dates and times in a variety of styles.
 See also: Time, Earth, Solar, Sun, Second
|
