Julian day

Julian day(Julian day) is refers by the A.D.Previous in 47131 month on 1st，□□world □Noon12 □□beginnings □□ day □, are many □Astronomy □family□uses, with by makes □an astronomy □□□law, difference□lawTimeline □together □.

The Julian day is one kind does not use the years long-term Ji Rifa, the simple form isJD. Is by France scholar Joseph Justus Scliger (1540 year-1609 year) in1583 year creates, this name is for commemorate him the father □□ Italy scholar Julius Caesar Scaliger (1484 year-1558 year).

The Julian day beginning subscribes inIn 4713(In astronomy records is -4712 year)1 month on 1stGreenwich Mean TimeMean noon（When world12:00), namely JD 0 assigns isUTTimeB.C.In 47131 month on 1st12:00 to UC time B.C.In 47131 month on 2nd12:00 24 hour. Every one day has entrusted with an only numeral, along number but under, for example:1996 year1 month on 1st 12:00:00 Julian day are 2.450084 million. This date was considers sun、MoonTrackThe movement cycle, as well as received at that timeTaxThe gap but subscribes. Joseph Scliger defines the Confucian cycle is in 7980 slightly, is because of 28, 19, 15Least common multiple numberFor 28×19×15=7980. Among:

28 years are oneSolar cycle(solar cycle), passes through a solar cycle, then week date foreword and month date foreword can duplicate.

19 years are oneMoon cycleOr name silent winter chapter (Metonic cycle), because of 235Lunar month=19 tropical year, passes through a moon cycle then lunar calendar month year date foreword is redundant.

15 years are oneYoung Ji(indiction cycle), this isRoman emperorConstantine(Constantine) proclaimed that, every 15 years evaluate the property value by to supply the assessment, become ancient Rome uses era unit,

Therefore take 7980 as oneConfucian slightly cycleBut elects beginning in 4713, then is the recent year which at the same time these three cycle period starts.

Counts Japan take the Julian day is separated by the date number as the convenience computation age which remote or the different calendar two events is separated.

Because the Julian day numeral figure too are many,International astronomy federationIn1973 year useSimplification Julian day(MJD), its definition is MJD = JD - 2400000.5. The MJD corresponding beginning is1858 year11 month on 17th world 0 o'clock.

Refers to

• Confucian slightly □ (Julian Date) is □□the Julian day □as soon as assigns □the fruit which small □adds together obtains, with the Julian day is the completely different concept.