In a situation where you are migrating existing data into CRM there is a good chance you will want to keep the same “createdon” date of the records in order to maintain an accurate history. If you are using a third party tool or writing code yourself, your first instinct is probably to match up the created date on the existing record to the “createdon” field of the CRM record type. If you are reading this you inevitably figured out that doesn’t work and you ended up with a created date of the date and time your process ran instead.
To resolve this, match up your existing created date to the the “overriddencreatedon” field in your CRM record type. Behind the scenes when records get created in this manner, the date you specify gets moved to the “createdon” field while the process date gets inserted into the “overriddencreatedon” field.
This applies to CRM 4.0 and CRM 2011.