Add cancel button for edit log.

Disable edit button for past month
Format gas correctly

Web/Models/DomainRules.cs

@@ -0,0 +1,27 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Web;
+
+namespace MileageTraker.Web.Models
+{
+	public static class DomainRules
+	{
+		/// <summary>
+		/// Returns the most recent date for which a log can be submitted from today
+		/// </summary>
+		public static DateTime GetLogEntryCutoff()
+		{
+			return GetLogEntryCutoff(DateTime.Today);
+		}
+
+		/// <summary>
+		/// Returns the most recent date for which a log can be submitted given the
+		/// reference date
+		/// </summary>
+		public static DateTime GetLogEntryCutoff(DateTime referenceDate)
+		{
+			return referenceDate.AddMonths(-1).AddDays(-referenceDate.Day + 1); // last two months
+		}
+	}
+}