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From: ralf@b.gp.cs.cmu.edu (Ralf Brown)
Newsgroups: comp.binaries.ibm.pc.d
Subject: Re: Looking for D.O.W. algorithm
Keywords: weekday
Message-ID: <6180@pt.cs.cmu.edu>
Date: 18 Sep 89 19:39:06 GMT
References: <6470@hubcap.clemson.edu> <1839@sactoh0.UUCP> <766@chyde.uwasa.fi> <1989Sep18.165034.19753@agate.berkeley.edu>
Organization: Carnegie-Mellon University, CS/RI
Lines: 24

In article <1989Sep18.165034.19753@agate.berkeley.edu> hughes@math.berkeley.edu (Eric Hughes) writes:
}>bios call only returns the *current* weekday, but for *any* weekday
}>an algorithm is needed.  
}
}The standard trick under MSDOS is to save the current date, then set
}the date to the desired one, get the day of the week, and finally
}reset the date to the real one.

Which of course is not too nice if you're running a multitasker and another
task asks for the date in the middle of the above process....

}Oh, and if you want to do this for dates previous to the 15th century,
}you'll need to take into account various calendar adjustments that
}were made. :-)

Don't forget to include a database of which adjustments were made when by
which countries (Russia didn't switch from Julian until early this century,
England and the at-that-time American colonies switched in 1752).

-- 
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