title: Update events json url when month/week is changed on Full Calendar
body: <p>Every time that I change the month or week I need that the json url link update.</p>
  
  <p>Example:</p>
  
  <p>Start Json url's is: </p>
  
  <pre><code>/json/?start=2018-01-28&amp;end=2018-03-10
  </code></pre>
  
  <p>When I changed to next month url change to: </p>
  
  <pre><code>/json/?start=2018-02-25&amp;end=2018-04-07
  </code></pre>
  
  <p>I tried to uptade url by storage, by getDate(), but didnt worked.</p>
  
  <p>My current code:</p>
  
  <pre><code>document.addEventListener('DOMContentLoaded', function() {
  
      var element = document.querySelector(".json-path");
  
      var jsonPath = element.innerText;
      $.ajax({
          type: 'GET',
          url: jsonPath,
          success: function(output) {
            let availability = output.availability
            calendar(availability);
            console.log(output);
         }
  
     });
  
  
     function calendar(availability){
        console.log(availability);
        let date = availability;
  
        $('#calendar').fullCalendar({
           header: {
           left: 'none',
           center: 'prev,title,next',
           right: 'month,agendaWeek'
        },
        height: 1000,
        navLinks: true,
        editable: false,
        eventLimit: true,
        selectHelper: true,
        businessHours: date,
        events: function(start,end,timezone,callback) {
            $.ajax({
              url: jsonPath,
              success: function(data) {
                var events = [];
                callback(data.events)
                console.log("Current path " + jsonPath);
            },
        });
      }
    });
  </code></pre>
  
  <p>EDIT:</p>
  
  <p>Currently I get current month/week with this code:</p>
  
  <pre><code>let day = document.querySelectorAll(".fc-day");
  
    let splitFirstDate = day[0].dataset.date.split('-');
  
    let getFirstYear = parseInt(splitFirstDate[0])
    let getFirstMonth = parseInt(splitFirstDate[1])
    let getFirstDay = parseInt(splitFirstDate[2])
  
    let splitLastDate = day[41].dataset.date.split('-');
  
    let getLastYear = parseInt(splitLastDate[0])
    let getLastMonth = parseInt(splitLastDate[1])
    let getLastDay = parseInt(splitLastDate[2])
  </code></pre>
  
  <p>After get the date I update the json path:</p>
  
  <pre><code>&lt;p class="json-path"&gt;{% url 'agenda-json' object.professional.pk object.pk %}?start=&lt;span class="start-date__year"&gt;&lt;/span&gt;&lt;span class="start-date__month"&gt;&lt;/span&gt;&lt;span class="start-date__day"&gt;&lt;/span&gt;&amp;end=&lt;span class="end-date__year"&gt;&lt;/span&gt;&lt;span class="end-date__month"&gt;&lt;/span&gt;&lt;span class="end-date__day"&gt;&lt;/span&gt;&lt;/p&gt;
  </code></pre>