How to correct person effective date for previous employment

We have a rehired employee whose person effective date is incorrect - it looks like his person record was added manually by a user at the time of rehire in 2015, but was created without date tracking back to his original start date.  So his person effective date matches his rehire date of 8/17/15.  His original start date of 6/9/08 was entered for Date First hired, but of course his person record doesn't exist prior to 8/17/15.

We're now trying to add historical records for employees (like training records in OLM) and cannot for him.  If we had realized this at the time I know a way to correct it would have been to just delete the person record and recreate using the correct data, but now he has two years worth of active history and going back to scratch isn't an option.