Cannot set overriddencreatedon when creating entity

Microsoft Dynamics CRM 2011 On premise.

According to http://mostlymscrm.blogspot.co.uk/2012/07/understanding-createdon-and.htmloverriddencreatedon can be set when creating a new record to override the default value for createdon.

I am using Simego Data Synchronisation Studio to create some records in CRM and when I set the value of overriddencreatedon to one date time value, the UTC date time when the record was created is used instead.