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

Other days

lisp

Lisp Day
coffee

Coffee Day
self appreciation

Self Appreciation Day
blanket fort

Blanket Fort Day
youth

Youth Day
boba

Boba Day
artists

Artists Day
self care

Self Care Day
my little pony

My Little Pony Day
bow tie

Bow Tie Day