Android : how to set alarm to repeat monthly

Currently I am working on an application to set reminders on monthly basis. I am not able to provide the correct repeating interval for my alarmmanager. Pls provide info about the same. this is my code, but this will not raise alarm for Feb or months having 30 days.

repeatTime=(AlarmManager.INTERVAL_DAY*31);
mAlarmManager.setRepeating(AlarmManager.ELAPSED_REALTIME_WAKEUP, when.getTimeInMillis(), repeatTime, pi);

Thanks, Sharath