P5js-calendar-weekday

var myDate = new Date();
var wochentag = new Array(7);
var myWochentag;
var tomorrow;

function setup() {
  createCanvas(400, 400);

  wochentag[0] = "Sonntag";
  wochentag[1] = "Montag";
  wochentag[2] = "Dienstag";
  wochentag[3] = "Mittwoch";
  wochentag[4] = "Donnerstag";
  wochentag[5] = "Freitag";
  wochentag[6] = "Sammstag";
  
  myDate.setYear(2017);
  myDate.setMonth(11); // 0 - 11
  myDate.setDate(31); // 1 - 31 (30,28 ...)
  
  tomorrow = new Date(myDate.getTime() + (24 * 60 * 60 * 1000));

  myWochentag = wochentag[myDate.getDay()];
}

function draw() {
  background(220);
  text(myDate + " = " + myWochentag, 10, 50);
  text(tomorrow, 10, 100);
}