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

Other days

ruby

Ruby Day
singles

Singles Day
fiancee

Fiancee Day
kiss a ginger

Kiss A Ginger Day
boba

Boba Day
gum

Gum Day
azonto is acceptable

Azonto Is Acceptable Day
coffee

Coffee Day
bounce

Bounce Day
pampering

Pampering Day