Using computed properties in queryParams

controllers.application.js

import Ember from 'ember';
import moment from 'moment';
const { computed } = Ember;

export default Ember.Controller.extend({
  queryParams: ['before'],
  
  before: '2017-08-23T03:55:00Z',
  
  beforeDate: computed('before', {
    get() {
      return moment(this.get('before'));
    },
    set(key, value) {
      this.set('before', value.format());
      return value;
    }
  }),
  
  actions: {
    updateExample() {
      let strValue = this.get('exampleInput');
      let newDate = moment(strValue);
      if (newDate.isValid()) {
        this.set('beforeDate', newDate);
        this.set('exampleInput', '');
      }
    }
  }
});

templates.application.hbs

<div class="hack container">
  <dl>
    <dt><code>before</code></dt>
    <dd>&ldquo;{{before}}&rdquo;</dd>
    
    <dt><code>beforeDate</code></dt>
    <dd>
      <time datetime={{moment-format beforeDate}}>
        {{moment-format beforeDate "L"}}
      </time>
    </dd>
  </dl>

	<div class="form">
    <fieldset class="form-group">
      <label for="example-input">Example:</label>
      {{input type="date" class="form-control" id="example-input" value=exampleInput}}
    </fieldset>
    
    <div class="form-actions">
      <button class="btn btn-primary btn-block" {{action "updateExample"}}>
        Update
      </button>
    </div>
  </div>
</div>

twiddle.json

{
  "version": "0.15.0",
  "EmberENV": {
    "FEATURES": {}
  },
  "options": {
    "use_pods": false,
    "enable-testing": false
  },
  "dependencies": {
    "hack_css": "https://cdnjs.cloudflare.com/ajax/libs/hack/0.8.0/hack.css",
    "jquery": "https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.js",
    "ember": "3.2.2",
    "ember-template-compiler": "3.2.2",
    "ember-testing": "3.2.2"
  },
  "addons": {
    "ember-data": "3.2.0",
    "ember-moment": "7.8.0"
  }
}