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

Other days

first love

First Love Day
self appreciation

Self Appreciation Day
slime

Slime Day
lumpy rug

Lumpy Rug Day
ruby

Ruby Day
comfy

Comfy Day
frozen yogurt

Frozen Yogurt Day
aloxolt

Aloxolt Day
self care

Self Care Day
tulip

Tulip Day