How can I parse a JSON string that would cause illegal C# identifiers?

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);