Oops, it doesn't look like 'plant tree day' is a national day..

Other days

slime

Slime Day
law

Law Day
aloxolt

Aloxolt Day
my little pony

My Little Pony Day
one

One Day
ruby

Ruby Day
azonto is acceptable

Azonto Is Acceptable Day
ormille

Ormille Day
pampering

Pampering Day
cuddle up

Cuddle Up Day