1 /* Time Keeping Bugs Abound! */
9 int is_leap_year(year_t year)
11 return (year % 400 == 0) ? 1 :
12 (year % 100 == 0) ? 0 :
13 (year % 4 == 0) ? 1 : 0;
16 int days_in_year(year_t year)
18 return 365 + is_leap_year(year);
21 int days_in_month(year_t year, month_t month)
23 static int mdays[] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
24 int days = mdays[month];
26 days += is_leap_year(year);
30 int weeks_in_month(year_t year, month_t month)
32 int start = start_of_month(year, month);
33 int days = days_in_month(year, month);
34 return ((start + days)-1) / 7 + 1;
37 wday_t day_of_week(year_t year, month_t month, day_t day)
39 static int tmp[] = {0, 3, 2, 5, 0, 3,
43 int start = year + year / 4
47 return (start + day) % 7;
50 wday_t start_of_month(year_t year, month_t month)
52 return day_of_week(year, month, 1);
55 void add_days(year_t *year, month_t *month, day_t *day, int days)
57 time_t time = mktime(&(struct tm){
58 .tm_year = *year-1900,
62 time += days*24*60*60;
63 struct tm *tm = localtime(&time);
64 *year = tm->tm_year+1900;
70 const char *month_to_str(month_t month)
72 static const char *map[] =
73 { "Jan", "Feb", "Mar", "Apr", "May", "Jun",
74 "Jul", "Aug", "Sep", "Oct", "Nov", "Dec", };
77 const char *month_to_string(month_t month)
79 static const char *map[] =
80 { "January", "February", "March", "April",
81 "May", "June", "July", "August",
82 "September", "October", "November", "December" };
86 const char *day_to_st(wday_t day)
88 static const char *map[] =
89 { "Su","Mo", "Tu", "We", "Th", "Fr", "Sa" };
92 const char *day_to_str(wday_t day)
94 static const char *map[] =
95 { "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat" };
98 const char *day_to_string(wday_t day)
100 static const char *map[] =
101 { "Sunday", "Monday", "Tuesday", "Wednesday",
102 "Thursday", "Friday", "Saturday" };
109 printf("Year Month Start Weeks Days\n");
110 for (int y = 2012; y <= 2012; y++)
111 for (int m = JAN; m <= DEC; m++) {
113 printf("%-10s", month_to_string(m));
114 printf("%-6s", day_to_str(start_of_month(y,m)));
115 printf("%-6d", weeks_in_month(y,m));
116 printf("%-2d", days_in_month(y,m));