Oops, it doesn't look like 'post a pic of the sky on snap day' is a national day..

Other days

artists

Artists Day
prosecco

Prosecco Day
nae nae

Nae Nae Day
carpenters

Carpenters Day
nail polish

Nail Polish Day
gum

Gum Day
self appreciation

Self Appreciation Day
singles

Singles Day
self care

Self Care Day
ormille

Ormille Day