code: protected final void scheduleUpdate(long scheduledUpdateTimeMillis) {
          getSharedPreferences().edit()
                  .putLong(PREF_SCHEDULED_UPDATE_TIME_MILLIS, scheduledUpdateTimeMillis).apply();
          setUpdateAlarm(scheduledUpdateTimeMillis);
      }
docs: Schedules an update for some time in the future. Any previously scheduled updates will be
  replaced. When the update time elapses, {@link #onUpdate(int)} will be called with
  {@link #UPDATE_REASON_SCHEDULED}.
  
  <p> Note that this is persisted across device reboots, but only triggers after a subscriber
  subscribes to the source after reboot. The Muzei Live Wallpaper will re-subscribe to sources
  after reboot if it's the active wallpaper.
  
  @param scheduledUpdateTimeMillis The absolute scheduled update time, based on {@link
  System#currentTimeMillis()}. This value must be after
  the current time.