2 * Copyright (C) 2012 Andy Spencer <andy753421@gmail.com>
4 * This program is free software: you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation, either version 3 of the License, or
7 * (at your option) any later version.
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
14 * You should have received a copy of the GNU General Public License
15 * along with this program. If not, see <http://www.gnu.org/licenses/>.
18 /* Time Keeping Bugs Abound! */
26 int is_leap_year(year_t year)
28 return (year % 400 == 0) ? 1 :
29 (year % 100 == 0) ? 0 :
30 (year % 4 == 0) ? 1 : 0;
33 int days_in_year(year_t year)
35 return 365 + is_leap_year(year);
38 int days_in_month(year_t year, month_t month)
40 static int mdays[] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
41 int days = mdays[month];
43 days += is_leap_year(year);
47 int weeks_in_month(year_t year, month_t month)
49 int start = start_of_month(year, month);
50 int days = days_in_month(year, month);
51 return ((start + days)-1) / 7 + 1;
54 wday_t day_of_week(year_t year, month_t month, day_t day)
56 static int tmp[] = {0, 3, 2, 5, 0, 3,
60 int start = year + year / 4
64 return (start + day + 1) % 7;
67 wday_t start_of_month(year_t year, month_t month)
69 return day_of_week(year, month, 0);
72 void add_days(year_t *year, month_t *month, day_t *day, int days)
74 time_t time = mktime(&(struct tm){
75 .tm_year = *year-1900,
79 time += days*24*60*60;
80 struct tm *tm = localtime(&time);
81 *year = tm->tm_year+1900;
86 void add_months(year_t *year, month_t *month, int months)
88 int total = *year*12 + *month + months;
94 const char *month_to_str(month_t month)
96 static const char *map[] =
97 { "Jan", "Feb", "Mar", "Apr", "May", "Jun",
98 "Jul", "Aug", "Sep", "Oct", "Nov", "Dec", };
101 const char *month_to_string(month_t month)
103 static const char *map[] =
104 { "January", "February", "March", "April",
105 "May", "June", "July", "August",
106 "September", "October", "November", "December" };
107 return map[month%12];
110 const char *day_to_st(wday_t day)
112 static const char *map[] =
113 { "Su","Mo", "Tu", "We", "Th", "Fr", "Sa" };
116 const char *day_to_str(wday_t day)
118 static const char *map[] =
119 { "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat" };
122 const char *day_to_string(wday_t day)
124 static const char *map[] =
125 { "Sunday", "Monday", "Tuesday", "Wednesday",
126 "Thursday", "Friday", "Saturday" };
134 printf(" Year Month Start Weeks Days\n");
135 for (int y = 2012; y <= 2012; y++)
136 for (int m = JAN; m <= DEC; m++) {
138 printf(" %-10s", month_to_string(m));
139 printf(" %-6s", day_to_str(start_of_month(y,m)));
140 printf(" %-6d", weeks_in_month(y,m));
141 printf(" %-2d", days_in_month(y,m));