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

Other days

martini

Martini Day
blanket fort

Blanket Fort Day
fiancee

Fiancee Day
lisp

Lisp Day
pampering

Pampering Day
youth

Youth Day
aloxolt

Aloxolt Day
lash

Lash Day
first love

First Love Day
ask out your crush

Ask Out Your Crush Day