You can deserialize to a dictionary.
public class Item
{
public string fajr { get; set; }
public string sunrise { get; set; }
public string zuhr { get; set; }
public string asr { get; set; }
public string maghrib { get; set; }
public string isha { get; set; }
}
var dict = JsonConvert.DeserializeObject<Dictionary<string, Item>>(json);