flot-weeks.js

/**
 * Get the ISO week date week number
 * Matthijs: implementation is not correct!
 * Added so you can grasp the idea
 */
Date.prototype.getWeek = function () {
	// Create a copy of this date object
	var target  = new Date(this.valueOf());

	// ISO week date weeks start on monday
	// so correct the day number
	var dayNr   = (this.getDay() + 6) % 7;

	// Set the target to the thursday of this week so the
	// target date is in the right year
	target.setDate(target.getDate() - dayNr + 3);

	// ISO 8601 states that week 1 is the week
	// with january 4th in it
	var jan4    = new Date(target.getFullYear(), 0, 4);

	// Number of days between target date and january 4th
	var dayDiff = (target - jan4) / 86400000;  

	// Calculate week number: Week 1 (january 4th) plus the  
	// number of weeks between target date and january 4th  
	var weekNr = 1 + Math.floor(dayDiff / 7);  // MLA removed "1 +"

	return weekNr;  
}

Date.prototype.nextWeek = function() {
  var copy = new Date(this.getTime());
  return new Date(copy.setDate(copy.getDate() + 7));
}

Date.prototype.beginningOfWeek = function() {
  var copy = new Date(this.getTime());
  var monday = new Date(copy.setDate(copy.getDate() - copy.getDay() + 1))
  monday.setHours(0)
  monday.setMinutes(0)
  monday.setSeconds(0)
  return monday;
}

$.plot($("#placeholder"), [data], {
xaxis: { 
  mode: "time", 
  ticks: function(axis) {
    var beginDate = new Date(axis.min),
        endDate = new Date(axis.max);

    var ticks = [];
    tickDate = beginDate.nextWeek().beginningOfWeek();
    while (tickDate < endDate) {
      ticks.push([tickDate.getTime(), "week " + tickDate.getWeek()]);
      tickDate = tickDate.nextWeek();
    }
    return ticks;
  },
} };

+1
Thank you!