[PATCH 16/16] cal: simplify day_in_week()

[Sami Kerola <kerolasa@iki.fi>]

The day_in_week() does not need to perform fullfledged September 1752
calculations, that month is dealt as static assignment.

Reported-by: Thomas Bächler <thomas@archlinux.org>
References: http://www.spinics.net/lists/util-linux-ng/msg07910.html
Signed-off-by: Sami Kerola <kerolasa@iki.fi>
---
 misc-utils/cal.c | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/misc-utils/cal.c b/misc-utils/cal.c
index 78f092d..d9b07bf 100644
--- a/misc-utils/cal.c
+++ b/misc-utils/cal.c
@@ -164,7 +164,6 @@ enum {
 };
 
 #define	FIRST_WEEKDAY		SATURDAY	/* Jan 1st, 1 was a Saturday */
-#define	REFORMATION_WEEKDAY	THURSDAY	/* after reformation it was Thursday */
 #define REFORMATION_YEAR	1752		/* Signed-off-by: Lord Chesterfield */
 #define REFORMATION_MONTH	9		/* September */
 #define	FIRST_MISSING_DAY	639799		/* 3 Sep 1752 */
@@ -702,9 +701,9 @@ static int day_in_year(int day, int month, int year)
 /*
  * day_in_week
  *	return the 0 based day number for any date from 1 Jan. 1 to
- *	31 Dec. 9999.  Assumes the Gregorian reformation eliminates
- *	3 Sep. 1752 through 13 Sep. 1752.  Returns Thursday for all
- *	missing days.
+ *	31 Dec. 9999.  Assumes the Gregorian reformation dates
+ *	3 Sep. 1752 through 13 Sep. 1752 are handled as statically
+ *	assigned array, see day_array().
  */
 static int day_in_week(int day, int month, int year)
 {
@@ -715,10 +714,10 @@ static int day_in_week(int day, int month, int year)
 	    leap_years_since_year_1(year - SMALLEST_YEAR)
 	    + day_in_year(day, month, year);
 	if (temp < FIRST_MISSING_DAY)
-		return ((temp - 1 + FIRST_WEEKDAY) % DAYS_IN_WEEK);
-	if (temp >= (FIRST_MISSING_DAY + NUMBER_MISSING_DAYS))
-		return (((temp - 1 + FIRST_WEEKDAY) - NUMBER_MISSING_DAYS) % DAYS_IN_WEEK);
-	return(REFORMATION_WEEKDAY);
+		return ((temp + (FIRST_WEEKDAY - 1)) % DAYS_IN_WEEK);
+	if (temp > FIRST_MISSING_DAY)
+		return ((temp + (FIRST_WEEKDAY - 1 - NUMBER_MISSING_DAYS)) % DAYS_IN_WEEK);
+	abort();
 }
 
 static char *ascii_day(const int julian, char *p, int day)
-- 
1.8.2.2