void set_system_time(time_t timestamp)
Initialize the system time. Examples are...
struct tm rtc_time; read_rtc(&rtc_time); rtc_time.tm_isdst = 0; set_system_time( mktime(&rtc_time) );
set_system_time(ntp_timestamp - NTP_OFFSET);
set_system_time(unix_timestamp - UNIX_OFFSET);