Adjusted age for late babies?

Lace01

I know for babies borm before their due date, you adjust the age and base their development off their due date, not their actual birth date.  Is it the same for babies born after their due date?  DS was 2 weeks late and seems to be hitting milestones 2 weeks "early."  I'm thinking he's just hitting them on time compared to an adjusted age.  Anyone know if that's how it works?  Thanks!