[Vautrin]

There is Sinterklaas of course (which later apparently became Santa Claus in many countries), which is on Novemer 5th. Centered around kids, a lot of legends and make-believe. Kids actually believe Sinterklaas is real.

Christmas of course. No Santa Claus then.
New Years, and Old Years. Nothing spectacular.
Queen's Day (30th of April). The Queen visits two cities in the country during that day. Everyone (at least those who support the monarchy) dresses up in orange, which is the Royal colour (it is in the name of the Royal family).

Carnival in the south of the country. It is relatively sober, compared to the carnivals in other countries. Although extensive booze consumption is involved.

4th of May, Memorial Day. For those fallen in wars
5th of May Liberation Day. To commemorate our Freedom (fall of the Third Reich)

And that is about it.

Most villages and towns of course have their own annual celebrations / festivities. Which also involve the consumption of thousands of litres of beer, averaging sometimes as much as 6 liters or so per inhabitant of the village, over a three day period. That includes the small kids, who don't drink of course.