A black man, tilting his head in satisfaction and checking it was about lunchtime, entered the Sphinx Café in downtown Washington D.C. on a Friday out of boredom with his usual lunch haunt and greeted the store owner. "Hey there, I'm Gabriel."
"Whoa, whoa, I think you shouldn't be working today! I'm Adrien."
"Why?" Gabriel retreated a little, for he had indeed gone to work today; a posh badge with his employment details hung from his neck.
"Aha…" came the reply with a sly smile. "That's for you to find out with today's special at the Sphinx Café: our new Puzzle Waffle! You'll have to assemble it first so there are no invisible holes though." Adrien brought out a prepared instance of the dish; it had twelve oddly shaped burr-like pieces and the ostensible target was printed on the accompanying tissue paper. "You want it?"
Numbers denote depth of notch, circled positions are marked with *
Pieces with one dividing line (...|...):
* E* *H H* *J *N J U** T*J*U 112233 312231 233212 132132 112332 133121
Pieces with two dividing lines (..|..|..):
331332 322312 133131 223312 312111 121222
"Sure, I'll take it." After waving his smartphone to pay, Gabriel sat down to solve the edible puzzle; he was very proud of who he was when done.
What day was it and why did Gabriel not need to work?
An accepted answer will include a workthrough of the Sudoku in this puzzle, which overall was inspired by Dan Fast's Web 6 puzzle. The notching pattern is different, though.