C++ 至1970-1-1的秒数转日期

bool IsLeap(int year) {
    if (year > 1970 && year < 9999) {
        if (year % 400 == 0 || year % 100 != 0 && year % 4 == 0)
            return true;
    }
    return false;
}

// 1970-1-1起始时间 格式：xxxx-xx-xx
std::string TimeToDate(int64_t time) {
    const char m_all_d[12] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
    int64_t total_day = time / (60 * 60 * 24);
    int year = 1970, month = 1, day = 1;

    while (year < 9999)
    {
        const int y_all_d = IsLeap(year) ? 366 : 365;

        if (total_day < y_all_d) {

            for (month = 1; month <= 12 && total_day > m_all_d[month - 1]; month++) {

                if (month == 2 && IsLeap(year))
                    total_day -= 29;
                else
                    total_day -= m_all_d[month - 1];

            }
            day += total_day;
            break;
        }
        else {
            total_day -= y_all_d;
            year++;
        }

    }

    return std::to_string(year) + '-' + std::to_string(month) + '-' + std::to_string(day);
}

最大年数我这里限制在9999年，to_string是C++11标准，需大于11标准才能编译的过。