Oops, it doesn't look like 'get some stomach day' is a national day..

Other days

carpenters

Carpenters Day
healing

Healing Day
bow tie

Bow Tie Day
prosecco

Prosecco Day
eat what you want

Eat What You Want Day
believe

Believe Day
offer

Offer Day
bounce

Bounce Day
youth

Youth Day
artists

Artists Day