Ds3231 alarm when date match

[odometer]

@david_2018

If you want an alarm on the last day of the month, presumably your code would need to set the day of the month properly.

int days_in_month (int y, int m) {
  // Fourth, eleventh, ninth, and sixth,
  // thirty days to each we fix. 
  if ((m==4)||(m==11)||(m==9)||(m==6)) return 30; 
  // Every other, thirty-one,
  // except the second month alone,
  if (m!=2) return 31;
  // which hath twenty-eight, in fine,
  // till leap-year give it twenty-nine.
  if ((y%400)==0) return 29; // leap year
  if ((y%100)==0) return 28; // not a leap year
  if ((y%4)==0)   return 29; // leap year
  return 28; // not a leap year 
}