From David’s Twitter:

The last moments of my hair being longer for the next couple of years

“Just before getting my haircut before I leave.”

It seems that the vlog was made yesterday, but not posted until today.  Richard, PapaFOD, indicates in his comment at FOD that David didn’t want any of the pictures taken of him yesterday posted until his vlog went up.    ~Vicki

So, thank you, David, for giving us a chance to say goodbye to your hair!