diff --git a/src/Variant.cpp b/src/Variant.cpp
index 08610fd61..cefbaf96c 100644
--- a/src/Variant.cpp
+++ b/src/Variant.cpp
@@ -277,10 +277,15 @@ bool Variant::operator< (const Variant& other) const
   case type_string:
     switch (right._type)
     {
-    case type_unknown:  throw std::string ("Cannot compare unknown type");
-    case type_boolean:  right.cast (type_string);  return left._string   < right._string;
-    case type_integer:  right.cast (type_string);  return left._string   < right._string;
-    case type_real:     right.cast (type_string);  return left._string   < right._string;
+    case type_unknown:
+      throw std::string ("Cannot compare unknown type");
+
+    case type_boolean:
+    case type_integer:
+    case type_real:
+      right.cast (type_string);
+      return left._string < right._string;
+
     case type_string:
       if (left.source () == "priority" || right.source () == "priority")
       {
@@ -293,6 +298,7 @@ bool Variant::operator< (const Variant& other) const
       {
         return left._string < right._string;
       }
+
     case type_date:     left.cast (type_date);     return left._date     < right._date;
     case type_duration: left.cast (type_duration); return left._duration < right._duration;
     }
@@ -301,26 +307,40 @@ bool Variant::operator< (const Variant& other) const
   case type_date:
     switch (right._type)
     {
-    case type_unknown:  throw std::string ("Cannot compare unknown type");
-    case type_boolean:  right.cast (type_date);    return left._date < right._date;
-    case type_integer:  right.cast (type_date);    return left._date < right._date;
-    case type_real:     right.cast (type_date);    return left._date < right._date;
-    case type_string:   right.cast (type_date);    return left._date < right._date;
-    case type_date:                                return left._date < right._date;
-    case type_duration:                            return left._date < right._duration;
+    case type_unknown:
+      throw std::string ("Cannot compare unknown type");
+
+    case type_boolean:
+    case type_integer:
+    case type_real:
+    case type_string:
+    case type_date:
+    case type_duration:
+      right.cast (type_date);
+      if (left._date == 0 || right._date == 0)
+        return false;
+
+      return left._date < right._date;
     }
     break;
 
   case type_duration:
     switch (right._type)
     {
-    case type_unknown:  throw std::string ("Cannot compare unknown type");
-    case type_boolean:  right.cast (type_duration); return left._duration < right._duration;
-    case type_integer:  right.cast (type_duration); return left._duration < right._duration;
-    case type_real:     right.cast (type_duration); return left._duration < right._duration;
-    case type_string:   right.cast (type_duration); return left._duration < right._duration;
-    case type_date:                                 return left._duration < right._date;
-    case type_duration:                             return left._duration < right._duration;
+    case type_unknown:
+      throw std::string ("Cannot compare unknown type");
+
+    case type_boolean:
+    case type_integer:
+    case type_real:
+    case type_string:
+    case type_date:
+    case type_duration:
+      right.cast (type_duration);
+      if (left._duration == 0 || right._duration == 0)
+        return false;
+
+      return left._duration < right._duration;
     }
     break;
   }
@@ -1661,19 +1681,21 @@ void Variant::cast (const enum type new_type)
     case type_date:
       {
         _date = 0;
-        ISO8601d iso;
-        std::string::size_type pos = 0;
-        if (iso.parse (_string, pos) &&
-            pos == _string.length ())
-        {
-          _date = (time_t) iso;
-        }
-        // Support legacy date formats.
-        else if (dateFormat != "")
+        if (dateFormat != "")
         {
           Date d (_string, dateFormat);
           _date = d.toEpoch ();
         }
+        else
+        {
+          ISO8601d iso;
+          std::string::size_type pos = 0;
+          if (iso.parse (_string, pos) &&
+              pos == _string.length ())
+          {
+            _date = (time_t) iso;
+          }
+        }
       }
       break;
     case type_duration: