Using RTC for 'daily maximum' temperature?

just added the RTC widget to my HVAC controller, but not sure how to ask for maximum since midnight?

here is where i am at so far:

void dataExtremesDaily()
{ //sets the maximum and minimum readings every 30 minutes ( via: timer.setInterval(30L * 60000L, dataExtremesDaily in the setup); )
  int houseTempMaxDaily;

  if (hour() + minute() > 82) // how do i get it to reset data at midnight?
  {
    houseTempMaxDaily = 0;
  }
  
  //max daily house temperature (from 00:00:01am)
  if (houseTempMaxDaily >= houseTemp)
  {
    houseTempMaxDaily = houseTempMaxDaily;
  }
  else if (houseTempMaxDaily < houseTemp)
  {
    houseTempMaxDaily = houseTemp;
  }
}

Our HVAC system checks at hourly intervals for firmware updates between 3am and 4am with:

void CheckFirmware(){
  if((hour() > 2) && (hour() < 5)) {  // check twice between 3am and 4am 
    #ifdef DEBUG
      Serial.println("Checked F/W 3am to 4am");
    #endif
    internetfirmware();
  }  
}

Not sure I follow your:

if (hour() + minute() > 82)

With your 30 minute timer I guess something like this would work for ‘midnight’.

if ((hour() == 0) && (minute() < 31)){
   // do something
}

As you might gather it can’t do anything at precisely midnight with a 30 minute timer, so it will be some time between midnight and 00:30.