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

Other days

singles

Singles Day
cuddle up

Cuddle Up Day
ormille

Ormille Day
pampering

Pampering Day
artists

Artists Day
kiss a ginger

Kiss A Ginger Day
stud

Stud Day
pick me

Pick Me Day
my little pony

My Little Pony Day
self care

Self Care Day