People have parties when they get a 25th birthday or 50th birthday, to mark the quarter- or half-century. Some people have celebrations to mark a third of a century.
Why not mark other fractions?
It seems that sometime in the very late evening on Tuesday 5th August, I'll reach the age of forty-two and six sevenths... which is exactly three-sevenths of a century. Hmmm.
See you all at the Tun on the seventh.