Ember: Model's property changes not detected in computed property

I have 2 models.

models/calendar.js

export default Model.extend({
  holidays: hasMany('holiday'),
  date: attr(),
  occasion: attr()
})

models/holiday.js

export default Model.extend({
  calendar: belongsTo('calendar')
})

And a component.

holidays/component.js

export default Component.extend({
  init() {
    this._super(...arguments);
    this.store.findAll('calendar')
      .then(calendar => this.set('calendar', calendar));
  },

  calendarIsDirty: computed('calendar.holidays.@each.{date,occasion}', function () {
    // This is not executed
  })
})

holidays/template.hbs

  
  



  <button>Save</button>

I'm displaying the holidays in the UI and when the user edits the date or occasion of the holiday, I want to do something. But the computed property that listens to these changes is not executed at all. Kindly help me with this.

I have an 'Add Holiday' button that adds an empty holiday that the user can edit. When I add a holiday, that computed property is executed. Only when I make changes to an existing holiday, the computed property is not executed.