1. C++标准库中的时间需要引用time.h，可以取的本地时间或者格林威治时间，只能精确到秒

#include <iostream>

/*包含time头文件*/
#include <time.h>

using namespace std;

int main()
{
    //time_t是long类型，精确到秒，是当前时间和1970年1月1日零点时间的差
    const time_t t = time(NULL);

    cout<<"current time is "<<t<<endl;

    /*本地时间：日期，时间 年月日，星期，时分秒*/
    struct tm* current_time = localtime(&t);
    printf("current year is %d;current month is %d;current date of month is %d\r\n",
        1900 + current_time->tm_year,
        1 + current_time->tm_mon/*此month的范围为0-11*/,
        current_time->tm_mday);

    printf("current day of year is %d;current day in week is %d\r\n",
        current_time->tm_yday,/*当前日期是今年的第多少天[0,365] */
        current_time->tm_wday/*days since Sunday - [0,6] */);

    printf("time part %d:%d:%d \r\n",
        current_time->tm_hour,
        current_time->tm_min,
        current_time->tm_sec);

    printf("\t本地时间：%d-%d-%d %d:%d:%d\r\n",
        current_time->tm_year + 1900,
        current_time->tm_mon + 1,
        current_time->tm_mday,
        current_time->tm_hour,
        current_time->tm_min,
        current_time->tm_sec);

    /*格林威治时间*/
    struct tm* current_gmtime = gmtime(&t);

    printf("格林威治时间：%d-%d-%d %d:%d:%d\r\n",
        current_gmtime->tm_year + 1900,
        current_gmtime->tm_mon + 1,
        current_gmtime->tm_mday,
        current_gmtime->tm_hour,
        current_gmtime->tm_min,
        current_gmtime->tm_sec);

    system("pause");
    return 0;
}

2. 系统时间 SYSTEMTIME 使用时要引用windows.h，可以精确到毫秒级别

#include <iostream>
#include <Windows.h>

int main(){
    //声明变量
    SYSTEMTIME sys_time;

    //将变量值设置为本地时间
    GetLocalTime( &sys_time );

    //输出时间
    printf( "%4d/%02d/%02d %02d:%02d:%02d.%03d 星期%1d\n",sys_time.wYear,
        sys_time.wMonth,
        sys_time.wDay,
        sys_time.wHour,
        sys_time.wMinute, 
        sys_time.wSecond,
        sys_time.wMilliseconds,
        sys_time.wDayOfWeek);

    system("time");

    system("pause");
    return 0;
}