Can I manually change the 'start date' to a date way back in the past, and then change the

We need to keep track of when a member joined our organization. So if they joined in Jan 1, 2003, can I change the start date to 2003-01-01, and the expiration date to their current expiration.

These are all one year memberships. If the woman renewed January 1, 2013, her expiry date would be January 1, 2014.

Would it hurt anything to manually change those?