Arduino Countdown Timer

/* Arduino Countdown Timer ~ www.boarduino.blogsot.com*/
#include <LiquidCrystal.h>
int jam = 0; //jam (hours)
int menit = 0; //menit (minutes)
int detik = 0; //detik (seconds)
int led = 13;
char hasil;
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

void setup() {
 lcd.begin(16, 2);
 Serial.begin(38400); //Baudrate adjust to your bluetooth module
 pinMode(13, OUTPUT);

    lcd.print("  Aktif Dalam:");
    lcd.setCursor(4, 2);
    (jam < 10) ? lcd.print("0") : NULL;
    lcd.print(jam);
    lcd.print(":");
    (menit < 10) ? lcd.print("0") : NULL;
    lcd.print(menit);
    lcd.print(":");
    (detik < 10) ? lcd.print("0") : NULL;
    lcd.print(detik);
    lcd.display();
}

void loop() {
  if(Serial.available() >0 ) {
   hasil = Serial.read();
   lcd.clear();
   delay(3);
   lcd.print("  Aktif Dalam:");
   lcd.setCursor(4, 2);
   (jam < 10) ? lcd.print("0") : NULL;
   (jam < 10) ? Serial.print("0") : NULL;
   lcd.print(jam);
   Serial.print(jam);
   lcd.print(":");
   Serial.print(" : ");
   (menit < 10) ? lcd.print("0") : NULL;
   (menit < 10) ? Serial.print("0") : NULL;
   lcd.print(menit);
   Serial.print(menit);
   lcd.print(":");
   Serial.print(" : ");
   (detik < 10) ? lcd.print("0") : NULL;
   (detik < 10) ? Serial.print("0") : NULL;
   lcd.print(detik);
   Serial.print(detik);
   lcd.display();
  }
  if(hasil == '1' ) {
    jam++;
    delay(200);
  } else if( jam > 24) {
    jam = 0;
    lcd.setCursor(4, 2);
   (jam < 10) ? lcd.print("0") : NULL;
   lcd.print(jam);
}
  if (hasil == '2') {
    jam-=1;
    delay(100);
  } else if ( jam < 0) {
    jam = 24;
    lcd.clear();
   delay(3);
   lcd.print("  Aktif Dalam:");
   lcd.setCursor(4, 2);
   (jam < 10) ? lcd.print("0") : NULL;
   lcd.print(jam);
   lcd.print(":");
   (menit < 10) ? lcd.print("0") : NULL;
   lcd.print(menit);
   lcd.print(":");
   (detik < 10) ? lcd.print("0") : NULL;
   lcd.print(detik);
   lcd.display();
}
if(hasil == '3' ) {
    menit++;
    delay(200);
  } else if( menit > 59) {
    menit = 0;
    lcd.setCursor(4, 2);
   (menit < 10) ? lcd.print("0") : NULL;
   lcd.print(menit);
}
  if (hasil == '4') {
    menit-=1;
    delay(200);
  } else if ( menit < 0) {
    menit = 59;
    lcd.clear();
   delay(3);
   lcd.print("  Aktif Dalam:");
   lcd.setCursor(4, 2);
   (jam < 10) ? lcd.print("0") : NULL;
   lcd.print(jam);
   lcd.print(":");
   (menit < 10) ? lcd.print("0") : NULL;
   lcd.print(menit);
   lcd.print(":");
   (detik < 10) ? lcd.print("0") : NULL;
   lcd.print(detik);
   lcd.display();
}
if(hasil == '5' ) {
    detik++;
    delay(200);
  } else if( detik > 59) {
    detik = 0;
    lcd.setCursor(4, 2);
   (detik < 10) ? lcd.print("0") : NULL;
   lcd.print(detik);
}
  if (hasil == '6') {
    detik-=1;
    delay(200);
  } else if ( detik < 0) {
    detik = 59;
    lcd.clear();
   delay(3);
   lcd.print("  Aktif Dalam:");
   lcd.setCursor(4, 2);
   (jam < 10) ? lcd.print("0") : NULL;
   lcd.print(jam);
   lcd.print(":");
   (menit < 10) ? lcd.print("0") : NULL;
   lcd.print(menit);
   lcd.print(":");
   (detik < 10) ? lcd.print("0") : NULL;
   lcd.print(detik);
   lcd.display();
}
if (hasil == '8') {
    jam = 0;
    menit = 0;
    detik = 0;
    lcd.setCursor(4, 2);
    (jam < 10) ? lcd.print("0") : NULL;
    lcd.print(jam);
    lcd.print(":");
    (menit < 10) ? lcd.print("0") : NULL;
    lcd.print(menit);
    lcd.print(":");
    (detik < 10) ? lcd.print("0") : NULL;
    lcd.print(detik);
    lcd.display();
  }
  else if(hasil == '7') {
    lcd.clear();
   delay(3);
   lcd.print("  Aktif Dalam:");
   lcd.setCursor(4, 2);
   (jam < 10) ? lcd.print("0") : NULL;
   (jam < 10) ? Serial.print("0") : NULL;
   lcd.print(jam);
   Serial.print(jam);
   lcd.print(":");
   Serial.print(" : ");
   (menit < 10) ? lcd.print("0") : NULL;
   (menit < 10) ? Serial.print("0") : NULL;
   lcd.print(menit);
   Serial.print(menit);
   lcd.print(":");
   Serial.print(" : ");
   (detik < 10) ? lcd.print("0") : NULL;
   (detik < 10) ? Serial.print("0") : NULL;
   lcd.print(detik);
   Serial.print(detik);
   lcd.display();

      hitungMundur();
      delay(1000);
     }
   }

void hitungMundur() {
    if (detik > 0) {
    detik -= 1;
    } else {
    if (menit > 0) {
    detik = 59;
    menit -= 1;
    } else {
    if (jam > 0) {
    detik = 59;
    menit = 59;
    jam -= 1;
    } else {
    aktif();
   }
  }
 }
}

void aktif() {
 lcd.clear();
 lcd.setCursor(5, 1);
 lcd.println("BOOM");
 digitalWrite(led, HIGH);
 delay(50);
 digitalWrite(led, LOW);
 delay(50);
 digitalWrite(led, HIGH);
 delay(50);
 digitalWrite(led, LOW);
 delay(50);
 digitalWrite(led, HIGH);
 delay(50);
 digitalWrite(led, LOW);
 delay(50);
 digitalWrite(led, HIGH);
 delay(50);
 digitalWrite(led, LOW);
 delay(10);
 lcd.display();
}