C++ time bomb

cpp_time_bomb

#include <ctime>
#include <iostream>
#include <string>
#include <sstream>

//-----------------------------------------------------------------------------
// Notes:
//  1) You should make full project rebuild during customer build
//  2) Keep error handling simple: just print message to cout and call exit(-1)
//  3) You can customize the number of days in evaluation period:

const double evaluation_period_in_days = 45.0;

//-----------------------------------------------------------------------------

using namespace std;

time_t time_when_compiled()
{
    // from: http://stackoverflow.com/questions/1765014/convert-string-from-date-into-a-time-t

    string datestr = __DATE__;
    string timestr = __TIME__;

    istringstream iss_date(datestr);
    string str_month;
    int day;
    int year;
    iss_date >> str_month >> day >> year;

    int month;
    if      (str_month == "Jan") month = 1;
    else if (str_month == "Feb") month = 2;
    else if (str_month == "Mar") month = 3;
    else if (str_month == "Apr") month = 4;
    else if (str_month == "May") month = 5;
    else if (str_month == "Jun") month = 6;
    else if (str_month == "Jul") month = 7;
    else if (str_month == "Aug") month = 8;
    else if (str_month == "Sep") month = 9;
    else if (str_month == "Oct") month = 10;
    else if (str_month == "Nov") month = 11;
    else if (str_month == "Dec") month = 12;
    else exit(-1);

    for(string::size_type pos = timestr.find(':'); pos != string::npos; pos = timestr.find(':', pos))
    {
    	timestr[pos] = ' ';
    }

    istringstream iss_time(timestr);
    int hour, min, sec;
    iss_time >> hour >> min >> sec;

    tm t = {0};
    t.tm_mon = month - 1;
    t.tm_mday = day;
    t.tm_year = year - 1900;
    t.tm_hour = hour;
    t.tm_min = min;
    t.tm_sec = sec;

    return mktime(&t);
}

//-----------------------------------------------------------------------------

int main()
{
    time_t current_time = time(NULL);
    time_t build_time = time_when_compiled();

    double diff_time = difftime(current_time, build_time);
    const double evaluation_period = evaluation_period_in_days * 24.0 * 60.0 * 60.0; // in seconds

    if(diff_time > evaluation_period)
    {
        cout << "Evaluation period has expired." << endl;
        exit(-1);
    }

    return 0;
}

//-----------------------------------------------------------------------------