De-Serialize json to dictionary not working properly

I am using NewtonSoft's JsonConvert.DeserializeObject<AppraiserCalendarDto>(content) method and am trying to de-serialize the following content to find out if a resource is working on particular date:

{
  "2017-05-18": {
    "regular": {
      "recordType": "working",
      "workTimeStart": "08:00",
      "workTimeEnd": "22:00"
    }
  },
  "2017-05-19": {
    "regular": {
      "recordType": "working",
      "workTimeStart": "08:00",
      "workTimeEnd": "22:00"
    }
  },
  "2017-05-22": {
    "regular": {
      "recordType": "working",
      "workTimeStart": "08:00",
      "workTimeEnd": "22:00"
    }
  },
  "2017-05-23": {
    "regular": {
      "recordType": "working",
      "workTimeStart": "08:00",
      "workTimeEnd": "22:00"
    }
  },
  "2017-05-24": {
    "regular": {
      "recordType": "working",
      "workTimeStart": "08:00",
      "workTimeEnd": "22:00"
    }
  },
  "2017-05-25": {
    "regular": {
      "recordType": "working",
      "workTimeStart": "08:00",
      "workTimeEnd": "22:00"
    }
  },
  "2017-05-26": {
    "regular": {
      "recordType": "working",
      "workTimeStart": "08:00",
      "workTimeEnd": "22:00"
    }
  },
  "links": [
    {
      "rel": "canonical",
      "href": "https://api.somedomain.com/rest/core/v1/resources/workSchedules/calendarView?dateFrom=2017-05-18&dateTo=2017-05-28"
    },
    {
      "rel": "describedby",
      "href": "https://api.somedomain.com/rest/core/v1/metadata-catalog/resources"
    }
  ]
}

My model class to be populated is as follows:

public class AppraiserCalendarDto
{
    public Dictionary<DateTime, Record> Records { get; set; }

    public class Record
    {
        [JsonProperty("recordType")]
        public string RecordType { get; set; }

        [JsonProperty("workTimeStart")]
        public TimeSpan WorkTimeStart { get; set; }

        [JsonProperty("workTimeEnd")]
        public TimeSpan WorkTimeEnd { get; set; }
    }

    public List<Link> Links { get; set; }

    public class Link
    {
        [JsonProperty("rel")]
        public string Rel { get; set; }

        [JsonProperty("href")]
        public string Href { get; set; }
    }
}

Unfortunately only the List<Link> Links gets populated and the Records dictionary is null.

I tried using Dictionary<string, Record> instead of Dictionary<DateTime, Record> with the same result.

Any feedback is greatly appreciated.