Using string for airdate instead of DateTime in models to prevent timezone issues

Fixed: Manual search air by date shows can now be sent to download client

src/NzbDrone.Core/Parser/InvalidDateException.cs

@@ -0,0 +1,19 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using NzbDrone.Common.Exceptions;
+
+namespace NzbDrone.Core.Parser
+{
+    public class InvalidDateException : NzbDroneException
+    {
+        public InvalidDateException(string message, params object[] args) : base(message, args)
+        {
+        }
+
+        public InvalidDateException(string message) : base(message)
+        {
+        }
+    }
+}