does std::get_time have a bug?

I'm solving a problem on a site. My code is the following:

string timeConversion(string s) {
    std::tm t = {};
    string result = "";
    std::istringstream ss(s);
    
    ss >> std::get_time(&t, "%I:%M:%S%p");
    if (ss.fail()) {
        std::ostringstream oss;
        oss << std::put_time(&t, "%H:%M:%S")  << endl;
        result = oss.str();
    } else {
        result = "Parse failed";
    }
    
    return result;
}

When I input 07:05:45PM it returns 07:05:45. But I expect 19:05:45. What is wrong?

UPDATE

The code is wrong for "if" statement. It must be

string timeConversion(string s) {
    std::tm t = {};
    string result = "";
    std::istringstream ss(s);
    
    ss >> std::get_time(&t, "%I:%M:%S%p");
    if (ss.fail()) {
        result = "Parse failed";
    } else {
        std::ostringstream oss;
        oss << std::put_time(&t, "%H:%M:%S")  << endl;
        result = oss.str();
    }
    
    return result;
}

The code returns "Parse failed" for "07:05:45PM" (g++ 5.4.0) It's unexpected too.