You will find some support online for Saturday being 'Is' Day or The Meaning of 'Is' Day.
It was on August 17, 1998 that President Bill Clinton's testimony to a grand jury included these amazing sentences: "It depends upon what the meaning of the word 'is' is. If the—if he—if 'is' means is and never has been, that is not—that is one thing. If it means there is none, that was a completely true statement." Rumor has it that two grammarians in Britain and fully 10 in the United States went stark raving mad attempting to diagram those sentences.
The Blog of Days, being squarely located in the Family Section of the Internet, will not go into details about the Monica Lewinsky matter. It is enough to recount that Mr. Clinton said on January 26, 1998, "I did not have sexual relations with that woman, Miss Lewinsky. I never told anybody to lie, not a single time; never. These allegations are false." However, on the evening of August 17, 1998, after his grand jury testimony, a few weeks after the infamous blue dress was turned over to the special prosecutor's office, Mr. Clinton was back again on TV, acknowledging (quoting now the linked Wikipedia article) that his "relationship with Lewinsky which was 'not appropriate.'"
Saturday is also Thrift Store Day. We know people who used to say they shopped at a store called "Sally's" -- trying to obscure by this that they were actually shopping at a Salvation Army Thrift Store. These days, however, resale shops have become almost trendy. If this sends a mixed message -- at least -- about the state of the modern American economy, well, so be it.
The Woodstock Music Festival ended on August 17, 1969. Nearly half a million people made the trip to Yasgur's Farm in Bethel, New York (about 50 miles from the town of Woodstock proper, according to the linked article on Usual Suspect History.com). Nearly 10 times that number claim to have been there.
Maureen O'Hara turns 93 on August 17. Robert De Niro marks his 70th birthday on Saturday.
Davy Crockett was born on a mountaintop in Tennessee on August 17, 1786. The linked Wikipedia article takes no position on whether he kilt him a b'ar when he was only three, but it puts that song right in your head, doesn't it? Some of the Usual Suspects designate Saturday as Davy Crockett Day in honor of Mr. Crockett's natal day.