WITHIN the 3 months prior to expiry you present this to an Examiner and he will give you 24 months FROM THE EXPIRY.
WITHIN the last 12 months....so you could re-validate 1 day after the first year, and then not have to re-validate for almost 3 years...(assuming you fly 12 hours on this day, 6 as PIC, land and take off lots and fit an hour in with an instructor

)
Cheers
EA