New Twiddle

components.my-component.js

import Ember from 'ember';

export default Ember.Component.extend({
  startDate: null,
  
  didReceiveAttrs() {
    this._super(...arguments);
  },
  
  actions: {
  	updateStartDate(date) {
      this.onUpdateStartDate(date);
    }
  }
});

controllers.application.js

import Ember from 'ember';

export default Ember.Controller.extend({
  queryParams: ['startDate'],
  startDate: null
});

templates.application.hbs

<br>
<br>
{{#link-to (query-params startDate="2018-03-01")}}2018-03-01{{/link-to}}
{{#link-to (query-params startDate="2018-02-15")}}2018-02-15{{/link-to}}
<br>
<br>

{{my-component 
  startDate=startDate
  onUpdateStartDate=(action mut startDate)}}

templates.components.my-component.hbs

<div style="border: 1px solid grey;">	
  <strong>startDate:</strong>{{startDate}}
  <a {{action "updateStartDate" "2018-04-30"}}>2018-04-30</a>
</div>

twiddle.json

{
  "version": "0.13.0",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.js",
    "ember": "2.16.2",
    "ember-template-compiler": "2.16.2",
    "ember-testing": "2.16.2"
  },
  "addons": {
    "ember-data": "2.10.0"
  }
}