程序代码：

long long date_to_us(int year, int month, int day, int minute, int sec, int ms, int us)
{
    const int MONTH_DAYS[] = {0, 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334};
    long long tick;
    tick =((year % 4 == 0 && year % 100 != 0 || year % 400 == 0) && month > 2) ? 1 : 0;
    year--;
    tick += year * 365 + year / 4 - year / 100 + year / 400 + MONTH_DAYS[month] + day;
    tick *= 1440;
    tick += minute;
    tick *= 60;
    tick += sec;
    tick *= 1000;
    tick += ms;
    tick *= 1000;
    tick += us;
    return tick;
}