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

Other days

bubble bath

Bubble Bath Day
bow tie

Bow Tie Day
cursing

Cursing Day
promposal

Promposal Day
youth

Youth Day
hoodie

Hoodie Day
boba

Boba Day
prosecco

Prosecco Day
self appreciation

Self Appreciation Day
camera

Camera Day