Arduino Master Code

#include < Wire.h >
String time = "10:11";
boolean doubleDigits = false;

void setup() {
  Wire.begin();
  Serial.begin(9600);
}

void loop() {
  Serial.println(time);
  sendTime(time);
  int First2 = time.substring(0, 2).toInt();
  if (First2 > 9) {
    doubleDigits = true;
  }

  int Last2 = time.substring(3).toInt();
  if ((time.substring(3) == "00") && (time != "00:00")) {
    First2 = First2 - 1;
    Last2 = 59;
    if (doubleDigits == false) {
      time = "0" + String(First2) + ":" + String(Last2);
    } else {
      time = String(First2) + ":" + String(Last2);
    }
  } else if (time != "00:00") {
    Last2 = Last2 - 1;
    if (Last2 < 10) {
      if (doubleDigits == false) {
        time = "0" + String(First2) + ":0" + String(Last2);
      } else {
        time = String(First2) + ":0" + String(Last2);
      }
    } else {
      if (doubleDigits == false) {
        time = "0" + String(First2) + ":" + String(Last2);
      } else {
        time = String(First2) + ":" + String(Last2);
      }
    }
  }
  if (time.substring(1, 2) == ":") {
    time = "0" + time;
  }
  delay(1000);
}

void sendTime(String time) {
  Wire.beginTransmission(9); //transmit to device 9
  char buffer[32];
  time.toCharArray(buffer, 32);
  Wire.write(buffer);
  Serial.println(buffer);
  Wire.endTransmission(); //stops transmitting
}

//master