Julian Date conversions

goldnhwk · Feb 11, 2000

Hi - 

 

does anyone out there know how to convert dates to Julian in QBASIC???? 

 

- Vicki

carpeliam · Mar 17, 2000

well... it's been so long since I've actually worked in QBASIC

) so I can't remember how to do dates at all... what are you working with so far? What do you have already? There's probably a way to do it that isn't language-specific, I can probably help you if I know where you're at at the moment. Liam Morley <a href=mailto:lmorley@wpi.edu>lmorley@wpi.edu</a> <a href=

http://www.wpi.edu/~lmorley/>::

imotic ::</a>

robherc · Mar 18, 2000

Hmmm....I'm not sure on the Julian dates part....not remembering that calendar very well; but if you give me a description of the diff. between Julian & real-world I'm sure I could come up with a little more help for you

-Robherc <a href=mailto:robherc@netzero.net>robherc@netzero.net</a> <a href= shared.freeservers.com/searchmaster.html>SearchMaster Interface...11-in-1</a> Wanting to learn Assembler; please e-mail me any tutorials or links for it that are useful to you

Guest_imported · May 19, 2000

2.12. What is the Julian Period? -------------------------------- The Julian period (and the Julian day number) must not be confused with the Julian calendar. The French scholar Joseph Justus Scaliger (1540-1609) was interested in assigning a positive number to every year without having to worry about BC/AD. He invented what is today known as the "Julian Period". The Julian Period probably takes its name from the Julian calendar, although it has been claimed that it is named after Scaliger's father, the Italian scholar Julius Caesar Scaliger (1484-1558). Scaliger's Julian period starts on 1 January 4713 BC (Julian calendar) and lasts for 7980 years. AD 1998 is thus year 6711 in the Julian period. After 7980 years the number starts from 1 again. Why 4713 BC and why 7980 years? Well, in 4713 BC the Indiction, the Golden Number and the Solar Number were all 1. The next times this happens is 15*19*28=7980 years later, in AD 3268. Astronomers have used the Julian period to assign a unique number to every day since 1 January 4713 BC. This is the so-called Julian Day (JD). JD 0 designates the 24 hours from noon UTC on 1 January 4713 BC to noon UTC on 2 January 4713 BC. This means that at noon UTC on 1 January AD 2000, JD 2,451,545 will start. This can be calculated thus:         From 4713 BC to AD 2000 there are 6712 years.         In the Julian calendar, years have 365.25 days, so 6712 years         correspond to 6712*365.25=2,451,558 days. Subtract from this         the 13 days that the Gregorian calendar is ahead of the Julian         calendar, and you get 2,451,545. Often fractions of Julian day numbers are used, so that 1 January AD 2000 at 15:00 UTC is referred to as JD 2,451,545.125. Note that some people use the term "Julian day number" to refer to any numbering of days. NASA, for example, use the term to denote the number of days since 1 January of the current year. 2.12.1. Is there a formula for calculating the Julian day number? ----------------------------------------------------------------- Try this one (the divisions are integer divisions, in which remainders are discarded):    a = (14-month)/12    y = year+4800-a    m = month + 12*a - 3   For a date in the Gregorian calendar:    JDN = day + (153*m+2)/5 + y*365 + y/4 - y/100 + y/400 - 32045   For a date in the Julian calendar:    JDN = day + (153*m+2)/5 + y*365 + y/4 - 32083 JDN is the Julian day number that starts at noon UTC on the specified date. The algorithm works fine for AD dates. If you want to use it for BC dates, you must first convert the BC year to a negative year (e.g., 10 BC = -9). The algorith works correctly for all dates after 4800 BC, i.e. at least for all positive Julian day numbers. To convert the other way (i.e., to convert a Julian day number, JDN, to a day, month, and year) these formulas can be used (again, the divisions are integer divisions):   For the Gregorian calendar:      a = JDN + 32045      b = (4*(a+36524))/146097 - 1      c = a - (b*146097)/4   For the Julian calendar:      b = 0      c = JDN + 32083   Then, for both calendars:      d = (4*(c+365))/1461 - 1      e = c - (1461*d)/4      m = (5*(e-1)+2)/153      day   = e - (153*m+2)/5      month = m + 3 - 12*(m/10)      year  = b*100 + d - 4800 + m/10 2.12.2. What is the modified Julian day number? ----------------------------------------------- Sometimes a modified Julian day number (MJD) is used which is 2,400,000.5 less than the Julian day number. This brings the numbers into a more manageable numeric range and makes the day numbers change at midnight UTC rather than noon. MJD 0 thus started on 17 Nov 1858 (Gregorian) at 00:00:00 UTC.

MiggyD · Jun 30, 2000

Hey goldnhwk, I've just happened to have gone through my old BASes and came across a few I got off the web. And in one of them, I came across the following code (which you should be able to modify to your lit'l heart's content.) DECLARE FUNCTION DateToJulian! (Dat$) FUNCTION DateToJulian! (Dat$) '******************************************************************************* '*  converts gregorian-style mm/dd/yyyy date to julian date                    * '*******************************************************************************     Month% = VAL(MID$(Dat$, 1, 2))     Day% = VAL(MID$(Dat$, 4, 2))     Year% = VAL(MID$(Dat$, 7, 4))     SELECT CASE Month%        CASE IS > 2           Month% = Month% - 3        CASE IS <= 2           Month% = Month% + 9           Year% = Year% - 1     END SELECT     A = 146097# * FIX(FIX(Year% / 100) / 4)     B = FIX(1461# * (Year% MOD 100) / 4)     C = FIX((153# * Month% + 2) / 5) + Day% + 1721119     DateToJulian = A + B + C END FUNCTION This may help I'm sure.  Especially since you don't have to type it all in. Just cut and paste away like me. I'm MiggyD (HEY THAT RHYMES, WHAT DO YA KNOW!?!?) [Note--couldn't resist the rhyming thing there.] <a href=mailto: > </a> <a href= > </a> If a tree falls in the forest and there's no one around, does it make sound? Its not the sound that matters, but the silence it leaves behind.

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Julian Date conversions

goldnhwk

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carpeliam

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robherc

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Guest_imported

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MiggyD

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