Manage leap seconds in time management

Question

I just learned that a leap second will be added at the end of this month (june 2015). I'm a little bit affraid about that, because I manage my own time class. I'm not sure it's robust enough.

I created a class Instant working with a unsigned long long int member variable ms which is the number of milliseconds from 01/01/1600 at 0:00:00.

When I want to get the current time, I call this function :

void Instant::setCurrentTime()
{
    struct timeval tv;
    gettimeofday(&tv, NULL);
    this->ms = NBR_DAYS_TO_EPOCH; // 135140
    this->ms *= NBR_SECONDS_IN_DAY; // 86400
    this->ms += tv.tv_sec;
    this->ms *= NBR_MILLISECONDS_IN_SECOND; // 1000
    this->ms += tv.tv_usec/1000;
}

My first question is : How leap seconds affect this number ? Is it already taken into account in the tv.tv_sec value ? How ?

My second question is about the conversion to human-readable format. I don't post it here because my function is quite huge (I can post it if required), but the idea is the following :

• I first compute the number of seconds in the current day, and then the number of minutes and hours ;
• I compute the number of days before the current day ;
• Then I compute the number of cycles of 400 years (periodic process), the number of cycles of 100 years in the current cycle of 400 years, and the number of cycles of 4 years in the current cycle of 4 years ;
• From that, I deduce the year (leap or not), the month, the day, and the day of the week ;
• Then I check if the summer time is activated, and I update the values according to the zone (europe, usa before 2007, usa from 2007) ;
• All of that without taking into account the 25 leap seconds added from 1970.

For the moment, my class is not able to say "we are 30/06/2015 at 23:59:60", because my number of seconds is limited to 59. But also because I don't know how to manage that. what could be a good way ?