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

Other days

hoodie

Hoodie Day
self appreciation

Self Appreciation Day
offer

Offer Day
my little pony

My Little Pony Day
eat what you want

Eat What You Want Day
youth

Youth Day
artists

Artists Day
boba

Boba Day
stud

Stud Day
healing

Healing Day