It's interesting how the customs about Sinterklaas / St. Nicholas varies in different countries around the world, sometimes it even varies within a country.
What I noticed: In the Netherlands and Aruba, Sinterklass and his assistants arrive mid/end of November by ship from Spain, they will stay until December 5 and travel back to Spain. During their stay they visit many homes and give out presents.
This is very different from most other traditions: In most other countries, St. Nicholas and his assistant will arrive on Dec 5 or Dec 6 (depending on each country) and will ONLY stay that day. Visit also homes and give out presents.
There can be different names like: Sinterklass (mainly in the Netherlands and Aruba) or Saint Nicholas or St. Nicholas. The name of his assistant can also vary.
When I grew up in Germany, we called him "Heiliger Nikolaus" and his assistant was called "Ruprecht". They would come on December 6 with the big book where all the good and bad deeds were written in. If a child was good, it would get a little present and some treats like apples, oranges, walnuts and chocolate. If a child was bad, Ruprecht would give him a spanking with the broom he was carrying. Children would also write a letter to Saint Nicholas with their wishes what they want the "Christ Kind" to bring on Christmas.
On Christmas, it would be the "Christ Kind" who would bring the presents on Christmas Eve, December 24. ONLY then was the beautifully Christmas Tree presented! Throughout December, there is a lot of joy and anticipation when FINALLY Christmas Eve would arrive! There is NO Christmas decoration or songs or anything before December.
On December 1 starts the Christmas Spirit. Streets and shops will be decorated, Christmas Markets will be held in many bigger towns throughout December, until December 24. The first candle of the Advenz wrath will be lit on the first Sunday of December, then the second, third and when the fourth candle is lit, it will be Christmas!
Christmas cookies will be baked in December, Gluehwein is prepared and drunk, Lebkuchen is availabe, the whole Christmas Spirit is present during December, all the good smells in the air, songs will be played, children at school practice to sing Christmas Carols, there are workshops where Christmas decoration is made. It's very beautiful and a true tradition!
As the Christmas Tree is actually put up on December 24, it is kept throughout the New Year until 6 January, which is the holiday of "The Holy Three Kings". There is a tradition to it as well, differing throughout countries. But that's for another story!