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

Other days

gum

Gum Day
youth

Youth Day
bubble bath

Bubble Bath Day
carpenters

Carpenters Day
singles

Singles Day
kale

Kale Day
tell a fairytale

Tell A Fairytale Day
bounce

Bounce Day
self appreciation

Self Appreciation Day
unicorn

Unicorn Day