In Ember 0.9, you might have a property that looks like

age: function() {
  return this.get('createdAt') - new Date();
}.property('createdAt').volatile()

The .property('createdAt') means, "recompute this every time createdAt changes".

The .volatile() means, "recompute this every time you get it."

That means that if we had a template,

Age: {{age}}

the template would be correct on render and when createdAt changes.

In Ember 1.0, this does not work. We need to do something more like

age: function() {
  return this.get('createdAt') - new Date();
}.property().volatile()

expireAge: function() {
  this.notifyPropertyChange('age');
}.observes('createdAt')

This project currently has no tools to aid this transition.