Reference: http://en.wikipedia.org/wiki/Determination_of_the_day_of_the_week#T.C3.B8ndering.27s_algorithm Signed-off-by: Sami Kerola <kerolasa@xxxxxx> --- misc-utils/cal.c | 50 ++++++++++++++++++++------------------------------ 1 file changed, 20 insertions(+), 30 deletions(-) diff --git a/misc-utils/cal.c b/misc-utils/cal.c index 4d45145..9575db4 100644 --- a/misc-utils/cal.c +++ b/misc-utils/cal.c @@ -234,8 +234,6 @@ int julian; /* function prototypes */ static int leap_year(int year); -static int centuries_since_1700(int year, int centuries); -static int leap_years_since_year_1(int year); static char * ascii_day(char *, int); static int center_str(const char* src, char* dest, size_t dest_size, size_t width); static void center(const char *, size_t, int); @@ -427,22 +425,6 @@ static int leap_year(int year) return ( !(year % 4) && (year % 100) ) || !(year % 400); } -/* number of centuries since 1700 */ -static int centuries_since_1700(int year, int n) -{ - if (year < REFORMATION_YEAR) - return 0; - else - return ((year / (100 * n)) - ((REFORMATION_YEAR / 100) / n)); -} - -/* number of leap years between year 1 and this year, not inclusive */ -static int leap_years_since_year_1(int year) -{ - return (year / 4 - centuries_since_1700(year, 1) + - centuries_since_1700(year, 4)); -} - static void headers_init(int julian) { int i, wd, spaces = julian ? J_DAY_LEN - 1 : DAY_LEN - 1; @@ -681,18 +663,26 @@ day_in_year(int day, int month, int year) { * during the period of 11 days. */ static int -day_in_week(int day, int month, int year) { - long temp; - - temp = - (long)(year - SMALLEST_YEAR) * DAYS_IN_YEAR + - leap_years_since_year_1(year - SMALLEST_YEAR) - + day_in_year(day, month, year); - if (temp < FIRST_MISSING_DAY) - return ((temp + (FIRST_WEEKDAY - 1)) % DAYS_IN_WEEK); - if (temp >= (FIRST_MISSING_DAY + NUMBER_MISSING_DAYS)) - return ((temp + (FIRST_WEEKDAY - 1 - NUMBER_MISSING_DAYS)) % DAYS_IN_WEEK); - return (NONEDAY); +day_in_week(int d, int m, int y) +{ + static const int reform[] = { + SUNDAY, WEDNESDAY, TUESDAY, FRIDAY, SUNDAY, WEDNESDAY, + FRIDAY, MONDAY, THURSDAY, SATURDAY, TUESDAY, THURSDAY + }; + static const int old[] = { + FRIDAY, MONDAY, SUNDAY, WEDNESDAY, FRIDAY, MONDAY, + WEDNESDAY, SATURDAY, TUESDAY, THURSDAY, SUNDAY, TUESDAY + }; + if (y != 1753) + y -= m < 3; + else + y -= (m < 3) + 14; + if (1752 < y || (y == 1752 && 9 < m) || (y == 1752 && m == 9 && 13 < d)) + return (y + (y / 4) - (y / 100) + (y / 400) + reform[m - 1] + + d) % 7; + if (y < 1752 || (y == 1752 && m < 9) || (y == 1752 && m == 9 && d < 3)) + return (y + y / 4 + old[m - 1] + d) % 7; + return NONEDAY; } static char * -- 1.8.2.3 -- To unsubscribe from this list: send the line "unsubscribe util-linux" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
