title: How to delete firebase data after "n" days
body: <p>I want do delete some old data from my Firebase, and I have a hard time do make it work.</p>
  
  <p>I tried this solution found here: <a href="https://stackoverflow.com/questions/15990681/firebase-chat-removing-old-messages">Firebase chat - removing old messages</a></p>
  
  <p>but this isn't deprecated.</p>
  
  <p>so I try it this way:</p>
  
  <pre><code>ChildEventListener childEventListener = new ChildEventListener() {
      @Override
      public void onChildAdded(DataSnapshot dataSnapshot, String s) {
  
          Calendar calendar = Calendar.getInstance();
          calendar.add(Calendar.DAY_OF_MONTH, -30);
  
          Log.d(TAG, "onChildAdded:" + dataSnapshot.getKey());
  
          String key = dataSnapshot.getKey();
  
          Marker retrievemarker =dataSnapshot.getValue(Marker.class);
          Calendar t3 = new           
          GregorianCalendar
          (c.get(Calendar.YEAR),
           c.get(Calendar.MONTH),
           retrievemarker.getSavedate());
  
          int date1= calendar.get(Calendar.DATE);
          int date2= t3.get(Calendar.DATE);
  
          Log.d("date1",""+date1);
          Log.d("date2",""+date2);
  
          if( date1 == date2 ){
  
              myRef.child(key).setValue(null);
  
          }
  </code></pre>
  
  <p>for explanation:
  In my Firebase I save a object named Marker, this object got a variable to store the savedate, the date where the object was saved in the Firebase.</p>
  
  <pre><code>int date = c.get(Calendar.DATE);
  marker.setSavedate(date);
  </code></pre>
  
  <p>I want to delete the object in the Firebase after 30 days. So I try to subtract 30 days from the Date Today than i want to compare this with the savedate from the Object if it equals i will delete the object from the Firebase.</p>
  
  <p>For the Subtraction I refer to an answer from the following question: <a href="https://stackoverflow.com/questions/212321/how-to-subtract-x-days-from-a-date-using-java-calendar">How to subtract X days from a date using Java calendar?</a></p>
  
  <p>But it doesn´t work. If I add a Object today to the Firebase the two dates are always equal. 
  So I guess the subtraction doesn´t work. </p>
  
  <p>What am I doing wrong?</p>