该程序简单地输入一个年份（1901年之后的年份），随后程序输出该年份十二个月的日历。

#include<stdio.h>#define Mon 1#define Tues 2#define Wed 3#define Thur 4#define Fri 5#define Sat 6#define Sun 0#define January_days 31#define February_days 28#define March_days 31#define April_days 30#define May_days 31#define June_days 30#define July_days 31#define August_days 31#define September_days 30#define October_days 31#define November_days 30#define December_days 31#define first1month January_days#define first2month January_days+February_days#define first3month January_days+February_days+March_days#define first4month January_days+February_days+March_days+April_days#define first5month January_days+February_days+March_days+April_days+May_days#define first6month January_days+February_days+March_days+April_days+May_days+June_days#define first7month January_days+February_days+March_days+April_days+May_days+June_days \ +July_days#define first8month January_days+February_days+March_days+April_days+May_days+June_days \ +July_days+August_days#define first9month January_days+February_days+March_days+April_days+May_days+June_days \ +July_days+August_days+September_days#define first10month January_days+February_days+March_days+April_days+May_days+June_days \ +July_days+August_days+September_days+October_days#define first11month January_days+February_days+March_days+April_days+May_days+June_days \ +July_days+August_days+September_days+October_days+November_daysint known_weekday = Tues;int known_year = 1901;int konwn_month = 1;int known_day = 1;int day_count(int month){ switch(month) { case 1: return 0;break; case 2: return first1month;break; case 3: return first2month;break; case 4: return first3month;break; case 5: return first4month;break; case 6: return first5month;break; case 7: return first6month;break; case 8: return first7month;break; case 9: return first8month;break; case 10: return first9month;break; case 11: return first10month;break; case 12: return first11month;break; }}/*char * month_name(int month){ switch(month) { case 1: return "January"; break; case 2: return "February"; break; case 3: return "March"; break; case 4: return "April"; break; case 5: return "May"; break; case 6: return "June"; break; case 7: return "July"; break; case 8: return "August"; break; case 9: return "September"; break; case 10: return "October"; break; case 11: return "November"; break; case 12: return "December"; break; default: break; }}*/char * month_name(int month){ switch(month) { case 1: return "一月"; break; case 2: return "二月"; break; case 3: return "三月"; break; case 4: return "四月"; break; case 5: return "五月"; break; case 6: return "六月"; break; case 7: return "七月"; break; case 8: return "八月"; break; case 9: return "九月"; break; case 10: return "十月"; break; case 11: return "十一月"; break; case 12: return "十二月"; break; default: break; }}void first_line_print(int month, int year){ //printf("%20s %d \n",month_name(month),year); printf("%8d年 %s \n",year, month_name(month));}void week_print(){ //printf("%-6s%-6s%-6s%-6s%-6s%-6s%-6s\n","Sun.", "Mon.", "Tues.", "Wed.", "Thur.", "Fri.", "Sat."); printf("%-3s%-3s%-3s%-3s%-3s%-3s%-3s\n","日", "一", "二", "三", "四", "五", "六");}int date_distance_count(int month, int year){ int leap_year_count = 0; int i; int distance; if (year > known_year) { for (i=known_year; i<year; i++) { if(((i%4 == 0) && (i%100 != 0) ) || (i%400 == 0)) { leap_year_count++; } } if (month > 2) { if(((year%4 == 0) && (year%100 != 0) ) || (year%400 == 0)) { leap_year_count++; } } } else if (year == known_year) { if (month > 2) { leap_year_count = 1; } } distance = (year - known_year)*365 + leap_year_count + day_count(month); return distance; }int makesure_firstday_weekday(int month, int year){ int date_distance = 0; int weekday; date_distance = date_distance_count(month, year); weekday = (known_weekday + date_distance)%7; return weekday; }void print_in_turn(int month, int firstday, int year){ int i = 1; int weekday; switch(firstday) { case Sun: break; case Mon: printf("%-3s",""); break; case Tues: printf("%-6s",""); break; case Wed: printf("%-9s",""); break; case Thur: printf("%-12s",""); break; case Fri: printf("%-15s",""); break; case Sat: printf("%-18s",""); break; } switch(month) { case 1: case 3: case 5: case 7: case 8: case 10: case 12: { for(i=0; i<31; i++) { weekday = (firstday + i)%7; printf("%-3d",i+1); if(weekday == Sat) { printf("\n"); } } break; } case 2: { if(((year%4 == 0) && (year%100 != 0) ) || (year%400 == 0)) { for(i=0; i<29; i++) { weekday = (firstday + i)%7; printf("%-3d",i+1); if(weekday == Sat) { printf("\n"); } } break; } else { for(i=0; i<28; i++) { weekday = (firstday + i)%7; printf("%-3d",i+1); if(weekday == Sat) { printf("\n"); } } break; } } case 4: case 6: case 9: case 11: { for(i=0; i<30; i++) { weekday = (firstday + i)%7; printf("%-3d",i+1); if(weekday == Sat) { printf("\n"); } } break; } }}void date_print(int month, int year){ int firstday; firstday = makesure_firstday_weekday(month, year); print_in_turn(month, firstday, year); printf("\n");}void main_month(int month, int year){ first_line_print(month, year); week_print(); date_print(month, year); printf("\n\n");}void main_calendar(int year){ int i; for(i=1; i<=12; i++) { main_month(i, year); }}int main(){ int year; printf("请输入年份：year = "); scanf("%d",&year); printf("\n"); while(year < 1902) { printf("请输入大于1901的年份\n"); printf("请输入年份：year = "); scanf("%d",&year); printf("\n"); } main_calendar(year); scanf(" "); return 0;}

运行效果图：