Oops, it doesn't look like 'hot fudge sundae hot fudge sundae day' is a national day..

Other days

pumpkin

Pumpkin Day

slime

Slime Day

ponytail

Ponytail Day

offer

Offer Day

artists

Artists Day

Me Day

boba

Boba Day

eat what you want

Eat What You Want Day

kiss a ginger

Kiss A Ginger Day

coffee

Coffee Day