1) The unit of 'Yonk' is known to be exactly 3 Months and 13 Days.
--> Used to describe a long period since you last saw someone or something. Usually termed 'Yonks' rather than a 'Yonk'.
BOB: "Gee Willy, I haven't seen you for Yonks!"
WILLY: "Yeah, must be about 3 Yonks actually."