1 #include <iostream>
2 #include <assert.h>
3
4
5 //判断是否闰年
6 bool IsLeapYear(unsigned int year)
7 {
8 if ((year % 4 == 0 && year % 100 != 0) || year % 400 == 0)
9 {
10 return true;
11 }
12 else
13 {
14 return false;
15 }
16 }
17
18 //根据一年中的第几天(0起始)，返回月份(1起始)，并且置天数为其在本月的索引(0起始)
19 unsigned int GetMonthByDay(unsigned int &day, bool leap)
20 {
21 assert(day < (leap ? 366 : 365));
22 static unsigned int monthtable[] = { 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
23 monthtable[1] = leap ? 29 : 28;
24
25 unsigned int month = 0;
26 unsigned int count = 0;
27 unsigned int n = day;
28
29 do
30 {
31 n = day - count;
32 count += monthtable[month++];
33 } while (day >= count);
34 day = n;
35 return month;
36 }
37
38 //距离1900年1月1日的天数(0起始)，返回年，并且置天数为其在本年的索引(0起始)
39 unsigned int GetYearByDay(unsigned int &day)
40 {
41 unsigned int Y = day / 365;
42 int D = day % 365;
43 int YY = Y - 1;
44 D -= YY / 4;
45 D += YY / 100;
46 D -= (YY + 300) / 400;
47 while (D < 0)
48 {
49 Y--;
50 D += IsLeapYear(Y + 1900) ? 366 : 365;
51 }
52 day = D;
53 return Y + 1900;
54 }
55
56 //距离1900年1月1日的天数(0起始)，计算这一天的日期(年，月，日)(1起始)。
57 void foo(unsigned int &day, unsigned int &year, unsigned int &month)
58 {
59 year = GetYearByDay(day);
60 month = GetMonthByDay(day, IsLeapYear(year));
61 day += 1;
62 }
63
64 int main()
65 {
66 unsigned int day = 42696;
67 unsigned int year = 0;
68 unsigned int month = 0;
69 foo(day, year, month);
70 std::cout << year << "/" << month << "/" << day << std::endl;
71 getchar();
72 return 0;
73 }
