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

Other days

bonang

Bonang Day
tulip

Tulip Day
martini

Martini Day
youth

Youth Day
kale

Kale Day
aloxolt

Aloxolt Day
gum

Gum Day
cuddle up

Cuddle Up Day
lumpy rug

Lumpy Rug Day
kiss a ginger

Kiss A Ginger Day