{

char buffer[11]; // 足够存放 "YYYY-MM-DD\0"

snprintf(buffer, sizeof(buffer), "%04d-%02d-%02d",

static_cast<int>(date.year()),

static_cast<unsigned>(date.month()),

static_cast<unsigned>(date.day()));

return std::string(buffer);

{

char buffer[9]; // 足够存放 "HH:MM:SS\0"

snprintf(buffer, sizeof(buffer), "%02d:%02d:%02d",

static_cast<int>(time.hours().count()),

static_cast<int>(time.minutes().count()),

static_cast<int>(time.seconds().count()));

return std::string(buffer);

{

std::istringstream iss(date_str);

int year, month, day;

char delim1, delim2;

if (!(iss >> year >> delim1 >> month >> delim2 >> day) ||

delim1 != '-' || delim2 != '-')

{

throw std::invalid_argument("Invalid date format. Expected YYYY-MM-DD");

}

return Date{

std::chrono::year{year},

std::chrono::month{static_cast<unsigned>(month)},

std::chrono::day{static_cast<unsigned>(day)}

};

{

std::istringstream iss(time_str);

int hours, minutes, seconds;

char delim1, delim2;

if (!(iss >> hours >> delim1 >> minutes >> delim2 >> seconds) ||

delim1 != ':' ||

delim2 != ':')

{

throw std::invalid_argument("Invalid time format. Expected HH:MM:SS");

}

return Time

{

std::chrono::hours{hours} +

std::chrono::minutes{minutes} +

std::chrono::seconds{seconds}

};