Dev C++ 6.3 编译通过：

Saturday
Sunday
Sunday
Saturday
Wednesday
Wednesday

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Process exited after 0.02175 seconds with return value 0
请按任意键继续. . .

基姆拉尔森公式

万能的日期计算公式，不用知道基准日是哪一天，也不需要判断year是否为闰年。

公式：weekday = (day+2month+3(month+1)/5+year+year/4-year/100+year/400+1)%7

注意：1月和2月需看做上一年的13月与14月，即 month<3时， year-=1; month+=12

Python代码

class Solution(object):def DayOfWeek(self, year, month, day):week = ["Sunday","Monday","Tuesday","Wednesday","Thursday","Friday","Saturday"]if month<3: year, month = year-1, month+12weekday = (day+2*month+3*(month+1)//5+year+year//4-year//100+year//400+1)%7return dict(zip(range(7),week)).get(weekday)if __name__ == "__main__":s = Solution()print(s.DayOfWeek(2019,8,31))print(s.DayOfWeek(1999,7,18))print(s.DayOfWeek(1993,8,15))print(s.DayOfWeek(1971,6,12))print(s.DayOfWeek(2023,2,22))print(s.DayOfWeek(2040,6,13))

Golang代码

package mainimport "fmt"func DayOfWeek(year int, month int, day int) string {week := []string{"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"}if month < 3 {year -= 1month += 12}weekday := (day + 2*month + 3*(month+1)/5 + year + year/4 - year/100 + year/400 + 1) % 7return week[weekday]
}func main() {fmt.Println(DayOfWeek(2019, 8, 31))fmt.Println(DayOfWeek(1999, 7, 18))fmt.Println(DayOfWeek(1993, 8, 15))fmt.Println(DayOfWeek(1971, 6, 12))fmt.Println(DayOfWeek(2023, 2, 22))fmt.Println(DayOfWeek(2040, 6, 13))}

C++代码

#include
using namespace std;class Solution
{
public:string DayOfWeek(int year, int month, int day){const char *week[7] = {"Sunday","Monday","Tuesday","Wednesday","Thursday","Friday","Saturday"};if (month < 3) {year -= 1;month += 12;} int weekday = (day+2*month+3*(month+1)/5+year+year/4-year/100+year/400+1)%7;return week[weekday];}
};int main()
{Solution s;cout << s.DayOfWeek(2019,8,31) << endl;cout << s.DayOfWeek(1999,7,18) << endl;cout << s.DayOfWeek(1993,8,15) << endl;cout << s.DayOfWeek(1971,6,12) << endl;cout << s.DayOfWeek(2023,2,22) << endl;cout << s.DayOfWeek(2040,6,13) << endl;return 0;
}

使用库函数

Python代码

datetime库

import datetimeclass Solution(object):def DayOfWeek(self, year, month, day):week = ["Sunday","Monday","Tuesday","Wednesday","Thursday","Friday","Saturday"]weekday = datetime.date(year,month,day).isoweekday()return week[weekday%7]if __name__ == "__main__":s = Solution()print(s.DayOfWeek(2019,8,31))print(s.DayOfWeek(1999,7,18))print(s.DayOfWeek(1993,8,15))print(s.DayOfWeek(1971,6,12))print(s.DayOfWeek(2023,2,22))print(s.DayOfWeek(2040,6,13))

calendar库 

import calendarclass Solution(object):def DayOfWeek(self, year, month, day):week = ["Sunday","Monday","Tuesday","Wednesday","Thursday","Friday","Saturday"]weekday = calendar.weekday(year,month,day)+1return week[weekday%7]if __name__ == "__main__":s = Solution()print(s.DayOfWeek(2019,8,31))print(s.DayOfWeek(1999,7,18))print(s.DayOfWeek(1993,8,15))print(s.DayOfWeek(1971,6,12))print(s.DayOfWeek(2023,2,22))print(s.DayOfWeek(2040,6,13))

Golang代码

time库，超级省事，连星期数组都不用了。

package mainimport ("fmt""time"
)func DayOfWeek(year int, month int, day int) string {return time.Date(year, time.Month(month), day, 0, 0, 0, 0, time.Local).Weekday().String()
}func main() {fmt.Println(DayOfWeek(2019, 8, 31))fmt.Println(DayOfWeek(1999, 7, 18))fmt.Println(DayOfWeek(1993, 8, 15))fmt.Println(DayOfWeek(1971, 6, 12))fmt.Println(DayOfWeek(2023, 2, 22))fmt.Println(DayOfWeek(2040, 6, 13))}

C++代码

ctime库

#include
#include
using namespace std;class Solution
{
public:string DayOfWeek(int year, int month, int day){const char *week[7] = {"Sunday","Monday","Tuesday","Wednesday","Thursday","Friday","Saturday"};struct tm t = {0};t.tm_year = year - 1900;t.tm_mon = month - 1;t.tm_mday = day;mktime(&t);return week[t.tm_wday%7];}
};int main()
{Solution s;cout << s.DayOfWeek(2019,8,31) << endl;cout << s.DayOfWeek(1999,7,18) << endl;cout << s.DayOfWeek(1993,8,15) << endl;cout << s.DayOfWeek(1971,6,12) << endl;cout << s.DayOfWeek(2023,2,22) << endl;cout << s.DayOfWeek(2040,6,13) << endl;return 0;
}

输出：

Saturday
Sunday
Sunday
Saturday
Wednesday
Sunday

--------------------------------
Process exited after 0.02402 seconds with return value 0
请按任意键继续. . .

发现没？ 2040.6.13返回的星期是错的！

网上查了资料，原来ctime库的CTime对象是有指定范围的：

static CTime WINAPI GetCurrentTime( );
获取系统当前日期和时间。

返回表示当前日期和时间的CTime对象。
int GetYear( ) const；
获取CTime对象表示时间的年份。

范围从1970年1月1日到2038年1月18日。

时间范围测试：

#include
#include
using namespace std;class Solution
{
public:string DayOfWeek(int year, int month, int day){const char *week[7] = {"Sunday","Monday","Tuesday","Wednesday","Thursday","Friday","Saturday"};struct tm t = {0};t.tm_year = year - 1900;t.tm_mon = month - 1;t.tm_mday = day;mktime(&t);return week[t.tm_wday%7];}
};int main()
{Solution s;for (int i=16;i<25;i++)cout << i << ":" << s.DayOfWeek(2038,1,i) << endl;return 0;
}

测试结果：

16:Saturday
17:Sunday
18:Monday
19:Tuesday
20:Sunday
21:Sunday
22:Sunday
23:Sunday
24:Sunday

--------------------------------
Process exited after 0.05159 seconds with return value 0
请按任意键继续. . .

2038.1.19日的星期也对，之后的全部返回Sunday。

修改这个问题，技术上一点问题都没有。 目前C++都发展到C++20了，而我用的是C++11，暂不知道之后版本的库文件有没有对此问题作过更新。那么，问题来了：

之前用C语言写的的软件，用ctime或者time.h获取时间的软件在2038年1月19日之后都会发生错误。还好，还有整整15年时间来改正这个“时间Bug”。