They change the name every so often to keep you guessing.
IIRC, they started as Baker Days after the twonk what allowed them, then they became PD(Professional Development) Days. I suspect its now gone to some localised 'Think of your own whizzy name' Day.
Looks up, bugger
...this is so you don't have 5 wasted days looking for 'Special Friends' who are actually at home being rogered by the au pair.