In case you didn't know, 12 March is Jolteon's Day.
I also don't know the origin of all these (Pokemon) Days but perhaps it began with the Japanese community
(For ex. Reshiram is 6 April, Eevee is 21 November, Sylveon is 21 February i think)
So... Happy Birthday to the Spiky Eeveelution! (An ideal present would be a tail)