trigger TaskTimeCalculation on Task_Tracker__c (before insert,before update) {
    
    //if(Trigger.isinsert && Trigger.isbefore)
   
    for (Task_Tracker__c t:Trigger.new){
        if(t.Status__c=='New')
            t.TaskOpened__c =system.now();
        
    }
  
    if(Trigger.isupdate && Trigger.isbefore){
        for(Task_Tracker__c ts:Trigger.new){
        
        Task_Tracker__c oldtask= Trigger.oldmap.get(ts.id);
            
            if(ts.Status__c=='New' && oldtask.Status__c!='new'){
                ts.TaskOpened__c=system.now();
            }
            
            if(ts.Status__c=='Completed' && oldtask.Status__c!='Completed' && ts.TaskOpened__c!=null ){
                
                
             ts.Actual_Time__c=(system.now().getTime()-ts.TaskOpened__c.getTime()/(1000*60*60));
                
            }
            }
    } 

}


I am gertting error last line..
Illegal assignment from Long to Datetime 
this is the error i am getting.. please help me to solve this querry.. and plzz provide me correct code

Thank you!!