Our most notable holiday is Koninginnedag aka Queen's Day.|
It falls on April 30th, alternatively the 29th if the 30th is a sunday.
There will be parties and events all day and all night all around the country, but as usual, Amsterdam will draw the buggest crowds.
Many Dutch people will dress in national colors (lots of orange, some red/white/blue), and many of the kids will spend their mornings at small fairs trying to sell old toys and household items in order to buy enormous amounts of candy in the afternoon.
All this usually results in kids being high on sugar all day and the adults being mostly good-natured & drunk, and somehow almost nobody gets hurt.
A shorter explanation would be that it more or less is our own orange version of Paddy's Day ;)
Definitely a recommendation.
I will leave further fleshing out to fellow Dutchies.
"Festivals, Sports, Concerts, Public Holidays..."