Hi JP
One customer solved this by _time_set / _time_get.
MFS already tries to write the date based on _time_get. If you synchronise the systems tick with the real time it should all work.
//Synchronise systems clock to real time clock
rtc_datetime_t datetime;
RTC_DRV_GetDatetime( FSL_RTCTIMER1, &datetime );
DATE_STRUCT date;
TIME_STRUCT time;
date.YEAR = datetime.year;
date.MONTH = datetime.month;
date.DAY = datetime.day;
date.HOUR = datetime.hour;
date.SECOND = datetime.second;
date.MILLISEC = 0;
_time_from_date(&date, &time);
_time_set(&time);
Regards
Daniel