Oops, it doesn't look like 'parks and sites in california are offering free admission day' is a national day..

Other days

Chocolate Milkshake Day

Carpenters Day

Self Care Day

My Little Pony Day

Nae Nae Day

Ride The Wind Day

China Day

Cuddle Up Day

African Immigrant And Refugee Hiv And Hep Awareness Day

Nail Polish Day