It’s Cute Kitten Picture Day!
And there’s even a word of the day: hebdomadal (heb-DOM-a-dul, adjective). It means “weekly” and comes from late Latin hebdomadalis, from Greek hebdomas, hebdomad- ‘the number seven, seven days,’ from hepta ‘seven.’
So one could say Cute Kitten Pictue Day is a hebdomadal event.