Add sort by start date for the tasks list

Fixes #3840

UI/Scheduler/NSArray+Scheduler.m

@@ -182,7 +182,41 @@
   return [selfTitle caseInsensitiveCompare: otherTitle];
 }
 
-- (NSComparisonResult) compareTasksEndAscending: (NSArray *) otherTask
+- (NSComparisonResult) compareTasksStartDateAscending: (NSArray *) otherTask
+{
+  NSComparisonResult result;
+  unsigned int selfTime, otherTime;
+
+  // Start date
+  selfTime = [[self objectAtIndex: taskStartDateIndex] intValue];
+  otherTime = [[otherTask objectAtIndex: taskStartDateIndex] intValue];
+  if (selfTime && !otherTime)
+    result = NSOrderedAscending;
+  else if (!selfTime && otherTime)
+    result = NSOrderedDescending;
+  else
+  {
+    if (selfTime > otherTime)
+      result = NSOrderedDescending;
+    else if (selfTime < otherTime)
+      result = NSOrderedAscending;
+    else
+    {
+      // Calendar ID
+      result = [[self objectAtIndex: taskFolderIndex]
+                  compare: [otherTask objectAtIndex: taskFolderIndex]];
+      if (result == NSOrderedSame)
+        // Task name
+        result = [[self objectAtIndex: taskTitleIndex]
+                    compare: [otherTask objectAtIndex: taskTitleIndex]
+                    options: NSCaseInsensitiveSearch];
+    }
+  }
+
+  return result;
+}
+
+- (NSComparisonResult) compareTasksEndDateAscending: (NSArray *) otherTask
 {
   NSComparisonResult result;
   unsigned int selfTime, otherTime;