Tweak isEqual: to make it more robust.

Clocker/Panel/Data Layer/TimezoneData.swift

@@ -431,7 +431,9 @@ class TimezoneData: NSObject, NSCoding {
         guard let compared = object as? TimezoneData else {
             return false
         }
-        return placeID == compared.placeID
+      
+      // Plain timezones might have similar placeID. Adding another check for timezone identifier.
+        return placeID == compared.placeID && timezoneID == compared.timezoneID
     }
 }