TimeSpan why are you being difficult?

Question updated, 1/17/12 11:30 am EST.

What i am trying to do is to make the pet's hunger(or food) decrease every 12 hours

so the user/player can feed it every now and then.

any help would be much appreciated.

  var monsterCurrentHunger: int = 100;

  var monsterMaxHunger: int = 100;

  var hungerTimerStarted: boolean = false;

  var monsterAlive: boolean = true;

  var saveTime: System.DateTime;

  var passedTime: System.TimeSpan;

  var hungryTime: System.TimeSpan; // need to make this into a constant of 12 hours

  function Update () {

      // recording the timer or start point

      if (hungerTimerStarted == false){

      saveTime = System.DateTime.Now;

      hungerTimerStarted = true;

      }

      // once timer started 

      if (hungerTimerStarted == true){

      passedTime = System.DateTime.Now - saveTime;  

          // every 12 hours hunger lose 10 point.

     /*error: This code here is what i want to do and don't know how to do it.

1, how to create a constant timespan of 12 hours? (the hungryTime var on top)

2, how to do the 3 line below:

• //error msg end

       if (passedTime => hungryTime) {
  
         monsterCurrentHunger -= (10 * (passedTime/hungryTime));
  
             hungerTimerStarted = false;
  
         }
  

        }
  

    }