How to convert a time into epoch time?

user_788171 0
Viewed 38556

Say I have a specific instant in time where I know the hour, minute, day, second, month, year, etc; how can I convert this epoch time (seconds since 1970)?

I can't use Boost, so please don't suggest a Boost solution.

time c++
5 Answers

Sample code to convert date string in some format to unix epoch time.

struct tm tm;
double dateInEpoch;

if (strptime("06 Jul 2022", "%d %b %Y", &tm)) {
    time_t curTime;
    struct tm * timeinfo;
                
    time(&curTime );
    timeinfo = localtime(&curTime);
                
    timeinfo->tm_year = tm.tm_year
    timeinfo->tm_mon = tm.tm_mon;
    timeinfo->tm_mday = tm.tm_mday;
        
    dateInEpoch = mktime( timeinfo );
}

For date format, please visit http://www.cplusplus.com/reference/ctime/strftime/

To test epoch date, visit https://www.epochconverter.com

user_15280610

mktime and memset is most portable for me:

struct tm t;
memset(&t, 0, sizeof(tm)); // Initalize to all 0's
t.tm_year = 112; // This is year-1900, so 112 = 2012
t.tm_mon = 8;
t.tm_mday = 15;
t.tm_hour = 21;
t.tm_min = 54;
t.tm_sec = 13;
time_t time_since_epoch = mktime(&t);
user_26820120
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