如何在C++中将"%Y%m%d“格式的字符串转换为time_t变量？

#include <iostream>
#include <ctime>
#include <sstream>
#include <iomanip>

time_t convertStringToTimeT(const std::string& dateStr) {
    std::tm tm = {};
    std::istringstream ss(dateStr);
    ss >> std::get_time(&tm, "%Y%m%d");
    
    if (ss.fail()) {
        throw std::runtime_error("Failed to parse date string");
    }
    
    return mktime(&tm);
}

int main() {
    try {
        std::string dateStr = "20230430";
        time_t timeValue = convertStringToTimeT(dateStr);
        std::cout << "Converted time_t value: " << timeValue << std::endl;
    } catch (const std::exception& e) {
        std::cerr << "Error: " << e.what() << std::endl;
    }
    
    return 0;
}

#include <ctime>
#include <sstream>
#include <iomanip>

time_t convertStringToUTCTimeT(const std::string& dateStr) {
    std::tm tm = {};
    std::istringstream ss(dateStr);
    ss >> std::get_time(&tm, "%Y%m%d");
    
    if (ss.fail()) {
        throw std::runtime_error("Failed to parse date string");
    }
    
    // Set timezone to UTC
    tm.tm_isdst = -1; // Let the system decide about DST
    return timegm(&tm); // Non-standard but widely available
}