: '
/*
 * NAME         : dayOfWeek - return the day of the week for a date
 *
 * USAGE        : dayOfWeek   
 *
 * ARGUMENTS    : 	- Only accepts dates in the format DD MM YYYY 
 *				  where DD is in the rage 1-31
 *				  MM is 1 (Jan) thru 12 (Dec)
 *				  YYYY is 1753 - 9999
 *				  
 *
 * DESCRIPTION  : dayOfWeek returns the named day for any given date after 1753
 *
 * NOTES        : 1753 is the year after the change to the Gregorian
 *		  calendar - it gets really complex if you try to handle
 *		  dates before this
 *
 * SEE ALSO     : The Zeller Algorithm here is adapted from an example in "SQL for Smarties"
 *		  by Joe Celko
 *
 */'

dayOfWeek()
{
    (
	/usr/bin/bc <<!

	    define f(y, m, d) {

		b = y;
		a = m - 2;

		if ( a <= 0 ) {
		    a = a + 12;
		    b = y - 1;
		}

		x = ((d + (13 * a - 1) / 5 + 5 * (b % 100) / 4 - 7 * b / 400) % 7) + 1;

		return(x);
}
	    f($3, $2, $1)
!
) 2>/dev/null | while read VAL
    do
	case "$VAL" in
	1)
	    /bin/echo "Sun"
	    ;;
	2)
	    /bin/echo "Mon"
	    ;;
	3)
	    /bin/echo "Tue"
	    ;;
	4)
	    /bin/echo "Wed"
	    ;;
	5)
	    /bin/echo "Thu"
	    ;;
	6)
	    /bin/echo "Fri"
	    ;;
	7)
	    /bin/echo "Sat"
	    ;;
	esac
    done
}

exit 0







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