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

Other days

pick me

Pick Me Day
fiancee

Fiancee Day
unicorn

Unicorn Day
bow tie

Bow Tie Day
gum

Gum Day
ruby

Ruby Day
youth

Youth Day
slime

Slime Day
promposal

Promposal Day
latina equal pay

Latina Equal Pay Day