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From: dc@gcm (Dave Caswell)
Newsgroups: comp.misc
Subject: Re: Julian Date/Day Number
Message-ID: <378@white.gcm>
Date: Sat, 14-Nov-87 18:08:36 EST
Article-I.D.: white.378
Posted: Sat Nov 14 18:08:36 1987
Date-Received: Sun, 15-Nov-87 22:41:39 EST
References: <557@astroatc.UUCP> <6205@ihlpa.ATT.COM>
Reply-To: dc@white.UUCP (Dave Caswell)
Organization: Greenwich Capital Markets, Greenwich, CT
Lines: 20
Keywords: Ceasar, Astronomy, Dates, Etc.

In article <6205@ihlpa.ATT.COM> rjh@ihlpa.UUCP (45261-Herber,R.J.) writes:
>I am including a program that computes the astronomical Julian Date
>using the Roman Catholic church's definition of when the switch
>between the Julian and the Georgian calendars occurred, i.e. Oct 4,
>1582 Old Style was followed by Oct 15, 1582 New Style.
>
Much complicated code follows.

I am including a version that couldn't care less when day one is; because
you will probably only be using it to find the number of days between two dates.

This is the code I use for "Julian dates".  Mail me if you can't, or don't
want to, write the inverse function(it's more than three lines).

julian(d, m, y)
int	d,m,y;
	if (m>2)
		return(1461 * y / 4 + 153 * (m+1) / 5 + d);
	return(1461 * (y-1) / 4 + 153 * (m+13) / 5 + d);
}