//Add the following function to RTClib.cpp:
//Baldarn and Edo
//http://hack.lenotta.com
//
uint8_t DateTime::dayOfYear() const {    
    uint16_t days = d;
    for (uint8_t i = 1; i < m; ++i)
        days += pgm_read_byte(daysInMonth + i - 1);
    if (m > 2 && yOff % 4 == 0)
        ++days;

    return days;
}