java - How to delete firebase data after "n" days -

i want delete old data friebase. knew question asked lot here, have still hard time make work.

i try solution found here:

firebase chat - removing old messages

but ist deprecated.

so try way:

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);          } 

for explanation: in firebase save object named marker, object got variable store savedate, date object saved in firebase.

int date = c.get(calendar.date); marker.setsavedate(date); 

i want delete object in firebase after 30 days. try subtract 30 days date today want compare savedate object if equals delete object firebase.

for substraction refer following answer:

how subtract x days date using java calendar?

but dosen´t work. if add object today firebase 2 dates allways equal. guess subtraction dosen´t work.

what doing wrong?

say have data structure nodes line this:

-kitqnxlqzqolnucb9sjaddclose   time: "thu apr 28 17:12:05 pdt 2016"   timestamp: 1461888725444 

each such node has timestamp property indicates when created. preferably you'd set property using server timestamp.

with data structure, can build query returns items older 30 days , removes them:

long cutoff = new date().gettime() - timeunit.milliseconds.convert(30, timeunit.days); query olditems = ttlref.orderbychild("timestamp").endat(cutoff); olditems.addlistenerforsinglevalueevent(new valueeventlistener() {     @override     public void ondatachange(datasnapshot snapshot) {         (datasnapshot itemsnapshot: snapshot.getchildren()) {             itemsnapshot.getref().removevalue();         }     }      @override     public void oncancelled(databaseerror databaseerror) {         throw databaseerror.toexception();     } });