Исправлено путём проверки текущего дня.
Calendar calendar = Calendar.getInstance();
//Setting time of the day (7 AM here) Notification will be sent everyday.
Calendar currentDate = Calendar.getInstance();
calendar.set(Calendar.HOUR_OF_DAY, 7);
calendar.set(Calendar.MINUTE, 00);
calendar.set(Calendar.SECOND, 0);
if(currentDate.after(calendar)){
Log.w("Added a day", "1");
calendar.add(Calendar.DATE, 1);
}