HR Personnel number hiring date

Hi,

We are a service company and using SAP since 2012, our controlling area and all parameters are valid since 2012. We are using FI, CO,MM and SD modules of SAP.

We had implemented HCM last year but did not really use it.

Now, we have decided to use HCM in SAP completely.

While creating employees, I got stuck.

Some of our employees have joined in 2005-2011 and we would like to maintain their hiring date to real.

What should I do?

I was told controlling area needs to be extended in the past by 7 years?

Is it advisable??

Thank You in advance