Ember - child component updating a property coming from query params via parent component

I am using Ember 1.13.0 and trying to update a property coming from query params in a child component.

In child component js, when "time" is not defined, I am setting it to 1200. If i log the value of "time" (this.get('time')) in child component, after i update it, i can see its value being updated. But its doesn't get through to parent component action.

So, why I am not able to get its value in parent, if its getting updated in child?

Top level component:

Parent component:

<div>hello</hello>

Parent component JS:

actions: {
 submit:function(){
  var t = this.get('time')
 }
}

Child component:

<div>Time is </div>

Child component JS:

currentTime: function(){
 if(this.get('time')){
  return time;
 } else {
    this.set('time','1200');
    return '1200'
 }
}.property()