DST_GetNextTransition.c

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#include                "FBLib_time.h"
 
dword DST_GetNextTransition(byte ruleOrdinal, byte ruleDay, byte ruleMonth, byte ruleHour, byte ruleMin, word ruleYear)
{
  TRACEENTER();
 
  word        tempDate;
  dword       returnDate;
  word        year;
  byte        month, day, weekDay;
 
  tempDate = TAP_MakeMjd(ruleYear, ruleMonth, 1);  //Get the first day of the transition month;
 
  TAP_ExtractMjd(tempDate, &year, &month, &day, &weekDay);
 
  tempDate = tempDate + ruleDay - weekDay;
 
  if(weekDay > ruleDay)
  {
    tempDate = tempDate + (ruleOrdinal * 7);
  }
  else
  {
    tempDate = tempDate + ((ruleOrdinal - 1) * 7);
  }
 
  TAP_ExtractMjd(tempDate, &year, &month, &day, &weekDay);
 
  if(month != ruleMonth) {tempDate = tempDate - 7;} //An ordinal of 5 can sometimes land in next month
 
  returnDate = ((tempDate & 0xffff) << 16) | ((ruleHour & 0xff) << 8) | (ruleMin & 0xff);
 
  TRACEEXIT();
  return returnDate;
}