Custom order nested ng-repeat-start

I've struggling with the following:

I have a nested Object that I need to sort with ng-repeat-start:

    $scope.docs = [{
        April 2014: 
        0: {
        year: 2014,
        day: 23,
        time: "20:35:45",
        id: 54,
        month: 4,
        total: 38.02400000000001 },
        1: {
        year: 2014,
        day: 12,
        time: "20:35:45",
        id: 54,
        month: 4,
        total: 11.02400000000001 }
    },{
        December 2015: 
        0: {
        year: 2015,
        day: 24,
        time: "10:34:41",
        id: 60,
        month: 12,
        total: 138.0420000001 },
        1: {
        year: 2015,
        day: 12,
        time: "11:05:17",
        id: 75,
        month: 12,
        total: 21.0545001 },
        2: {
        year: 2015,
        day: 12,
        time: "18:05:17",
        id: 78,
        month: 12,
        total: 158.21 }
    }
]

Now I need to Show the header (April 2014..etc) in a sorted manner. I've used: http://forum.ionicframework.com/t/generating-list-with-dividers-dynamically/341/11

And i creates the desired result with one issue: As ng-repeat does not filter OBJECTS, the headers are sorted alphabetically, which you could see would pose a problem.

So I tried to convert the object to an array using a filter based the following example: http://jsfiddle.net/JHL6X/

.filter('toArray', function () {
    'use strict';

    return function (obj) {
        if (!(obj instanceof Object)) {
            return obj;
        }
        var result = [];
        angular.forEach(obj, function(obj, key) {
            obj.$key = key;
            result.push(obj);
        });
        return result;
    }
})

And call it in several way, including this:

  <div class="list">
    <ul>
      <li class="item item-divider" ng-repeat="header in docs | toArray | orderBy:['-year','-month','-day','-time']">
        {{header.$key}}
        <li ng-repeat="doc in header">
          <p>{{doc.month}}<span> {{doc.year}}</span></p>
        </li>
      </ul>
  </div>

But only shows the header, but no items under them. Any ideas?

UPDATE: Using ng-repeat-start AND ng-repeat-end now shows all the data with its headers, but the ORDER is random and I can't find a way to arrange the headers properly (the content works with orderBy, but not the headers).