[C++] ctime–Finding Weekday

#include<iostream>
#include<ctime>
using namespace std;
int main() {
 tm time{0,0,0,21,1-1,2017-1900};
 mktime(&time);
 cout << time.tm_wday << endl;
 system("pause");
 return 0;
}

tm:
 int tm_sec; // seconds after the minute - [0, 60] including leap second
 int tm_min; // minutes after the hour - [0, 59]
 int tm_hour; // hours since midnight - [0, 23]
 int tm_mday; // day of the month - [1, 31]
 int tm_mon; // months since January - [0, 11]
 int tm_year; // years since 1900
 int tm_wday; // days since Sunday - [0, 6]
 int tm_yday; // days since January 1 - [0, 365]
 int tm_isdst; // daylight savings time flag