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From: jmd@ee.umr.edu (Jim Dumser)
Newsgroups: comp.binaries.ibm.pc.d
Subject: Re: (Astronomical) Julian Date Source Wanted
Message-ID: <2609@umriscc.isc.umr.edu>
Date: 18 Apr 91 13:03:18 GMT
References: <9873.2808dac2@ohstpy.mps.ohio-state.edu> <40790007@hpcvra.cv.hp.com.> <dfs.671832823@wesley>
Sender: news@umriscc.isc.umr.edu
Organization: University of Missouri - Rolla
Lines: 238

Well, don't know if this is Astronimical or USGov't Julian, but here are
some routines that were published in Computer Language (Dec 90).

There is also a discussion in the March 91 issue, which I haven't got to
yet, that covers these same routines.  I also thought there was a fix
published sometime inbetween Dec 90 and March 91, but I can't seem to
find it right now.

Jim

#! /bin/sh
# This is a shell archive.  Remove anything before this line, then unpack
# it by saving it into a file and typing "sh file".  To overwrite existing
# files, type "sh file -c".  You can also feed this as standard input via
# unshar, or by typing "sh <file", e.g..  If this archive is complete, you
# will see the following message at the end:
#		"End of shell archive."
# Contents:  date.c date.h
# Wrapped by jmd@franklin on Thu Apr 18 07:59:18 1991
PATH=/bin:/usr/bin:/usr/ucb ; export PATH
if test -f 'date.c' -a "${1}" != "-c" ; then 
  echo shar: Will not clobber existing file \"'date.c'\"
else
echo shar: Extracting \"'date.c'\" \(4477 characters\)
sed "s/^X//" >'date.c' <<'END_OF_FILE'
Xstatic char *rcsid = "$Id: date.c,v 1.1 1991/03/22 06:05:45 jmd Exp $";
X
X#include "date.h"
X
X
X/*
X * Calculate the Julian day number for a specified day, month, and year.
X * B.C. years are negative.
X */
X
XDATE julian_date(int day, int month, int year)
X  {
X    int a, b = 0;
X    float year_corr;
X
X    /* correct for negative year */
X    year_corr = (year > 0 ? 0.0 : 0.75);
X
X    if (month <= 2) {
X      year--;
X      month += 12;
X    }
X
X    /* cope with Gregorian calendar reform */
X    if (year * 10000.0 + month * 100.0 + day >= 15821015.0) {
X      a = year / 100;
X      b = 2 - a + a / 4;
X    }
X
X    return (DATE)((long)(365.25 * year - year_corr) +
X                  (long)(30.6001 * (month + 1)) + day + 1720994L + b);
X  }
X
X
X/*
X * Calculate the day, month, and year corresponding to a Julian day number.
X * B.C. years are negative.
X */
X
Xvoid calendar_date(DATE jdate, int *day, int *month, int *year)
X  {
X    long a, b, c, d, e, z, alpha;
X
X    z = jdate + 1;
X
X    /* cope with Gregorian calendar reform */
X    if (z < 2299161L) a = z;
X     else {
X      alpha = (long)((z - 1867216.25) / 36524.25);
X      a = z + 1 + alpha - alpha / 4;
X    }
X
X    b = a + 1524;
X    c = (long)((b - 122.1) / 365.25);
X    d = (long)(365.25 * c);
X    e = (long)((b - d) / 30.6001);
X    *day = (int)(b - d - (long)(30.6001 * e));
X    *month = (int)(e < 13.5 ? e - 1 : e - 13);
X    *year = (int)(*month > 2.5 ? c - 4716 : c - 4715);
X  }
X
X
X/*
X * Calculate the day of the week for the specified Julian day number:
X *   1 = Sunday, 2 = Monday, ..., 7 = Saturday
X */
X
Xint day_of_week(DATE date)
X  {
X    return (int)((date + 2) % 7 + 1);
X  }
X
X
X/*
X * Validate the specified day, month, and year.  For example, the following
X * dates are not valid:
X *   Feb 29, 1973		not a leap year
X *   Apr 31			April only has 30 days
X */
X
Xint valid_date(int day, int month, int year)
X  {
X    int cday, cmonth, cyear;
X
X    /* convert date to julian day number and back */
X    calendar_date(julian_date(day, month, year), &cday, &cmonth, &cyear);
X
X    /* date is valid if day, month, year didn't change */
X    return ((day == cday) && (month == cmonth) && (year == cyear));
X  }
X
X
X/*
X * Calculate the Julian day number of Easter for the specified year,
X * which can't be negative.
X */
X
XDATE easter(int year)
X  {
X    int a, b, c, d, e, f, g, h, i, k, l, m, n, p, day, month;
X
X    if (year >= 1583) {
X      /* Gregorian calendar */
X      a = year % 19;        b = year / 100;
X      c = year % 100;       d = b / 4;
X      e = b % 4;            f = (b + 8) / 25;
X      g = (b - f + 1) / 3;  h = (19 * a + b - d - g + 15) % 30;
X      i = c / 4;            k = c % 4;
X      l = (32 + 2 * e + 2 * i - h - k) % 7;
X      m = (a + 11 * h + 22 * l) / 451;
X      n = (h + l - 7 * m + 114) / 31;
X      p = (h + l - 7 * m + 114) % 31;
X      month = n;  day = p + 1;
X     } else {
X      /* Julian calendar */
X      a = year % 4;         b = year % 7;
X      c = year % 19;        d = (19 * c + 15) % 30;
X      e = (2 * a + 4 * b - d + 34) % 7;
X      f = (d + e + 114) / 31;
X      g = (d + e + 114) % 31;
X      month = f;  day = g + 1;
X    }
X
X    return julian_date(day, month, year);
X  }
X
X
X/*
X * Print a calendar for the specified month.
X */
X
Xvoid month_calendar(int month, int year)
X  {
X    DATE b_date, e_date, c_date, easter_d;
X    int day, c_day, c_month, c_year;
X
X    /* calculate Julian numbers for first and last days of the month */
X    b_date = julian_date(1, month, year);
X    if (month < 12) e_date = julian_date(1, month + 1, year) - 1;
X     else           e_date = julian_date(1, 1, year + 1) - 1;
X
X    printf("%2d/%d:\n\n", month, year);
X    printf("Sun Mon Tue Wed Thu Fri Sat\n\n");
X
X    /* put first day of month under correct day column */
X    for (day = 1; day < day_of_week(b_date); day++) printf("    ");
X    
X    /* print all the days */
X    for (c_date = b_date; c_date <= e_date; c_date++) {
X      calendar_date(c_date, &c_day, &c_month, &c_year);
X      printf("%3d ", c_day);
X      if (day_of_week(c_date) == 7) printf("\n");
X    }
X
X    /* if Easter happens this month, print the date */
X    easter_d = easter(year);
X    if (year >= 0 && easter_d >= b_date && easter_d <= e_date) {
X      calendar_date(easter_d, &c_day, &c_month, &c_year);
X      printf("\n\nEaster: %2d/%2d", c_month, c_day);
X    }
X
X    printf("\n\n\n");
X  }
X
X
X/*
X * Print a one-year calendar for the specified year.
X */
X
Xvoid year_calendar(int year)
X  {
X    int month;
X
X    for (month = 1; month <= 12; month++) month_calendar(month, year);
X  }
END_OF_FILE
if test 4477 -ne `wc -c <'date.c'`; then
    echo shar: \"'date.c'\" unpacked with wrong size!
fi
# end of 'date.c'
fi
if test -f 'date.h' -a "${1}" != "-c" ; then 
  echo shar: Will not clobber existing file \"'date.h'\"
else
echo shar: Extracting \"'date.h'\" \(462 characters\)
sed "s/^X//" >'date.h' <<'END_OF_FILE'
X/*
X * $Id: date.h,v 1.1 1991/03/22 06:05:45 jmd Exp $
X */
X
X
X/* Dates are represented as Julian day numbers, stored as long integers */
X
Xtypedef long DATE;
X
X
X/* ANSI prototypes */
X
XDATE julian_date(int day, int month, int year);
Xvoid calendar_date(DATE jdate, int *day, int *month, int *year);
Xint valid_date(int day, int month, int year);
Xint day_of_week(DATE date);
XDATE easter(int year);
Xvoid month_calendar(int month, int year);
Xvoid year_calendar(int year);
END_OF_FILE
if test 462 -ne `wc -c <'date.h'`; then
    echo shar: \"'date.h'\" unpacked with wrong size!
fi
# end of 'date.h'
fi
echo shar: End of shell archive.
exit 0