Established on this day because by the time December arrives, you'll always be blowing on your soup whenever you get to eat it!
There's a pun there:
Always blowing → itsumo fuufuu suru (lit. always doing fuu fuu) → itsu(mo) fu(u)fu(u suru) → i(1) tsu(2) fu(2) fu(2)The new maid (Cirno) blowing on her master's soup with all her might
