In the lesson it says:
As for the years post 2000's,
There is only one way to read them, and that is as a full number:
But there are still many years to come after the year 2000 (infinitely many actually).
So, how would you say 'the 10th of March 2155'? (my 200th birthday :)
"Le dix mars vingt et-un-cents cinquante cinq" or "Le dix mars deux mille deux cents cinquante cinq" (or neither)?