Newspaper Spits is running a poll that lets you select your favourite Prinsjesdag hat.
Prinsjesdag (Day of the Princes) is the day that the government presents its budget for the next year, that the Queen addresses a joint session of both chambers of parliament, and that is always held on the second Tuesday of the year. It is tradition for female parliamentarians to wear outrageous hats during the joint session.
And rather than holding Prinsjesdag on a Monday, Tuesday was chosen because in times before the introduction of railroads, it could take a representative more than a day to get to The Hague, and travelling on Sundays was frowned upon.
(More hats at NOS Journaal. Source screenshot: Spitsnieuws.nl.)