### Question:
DateUtil { public static final String formatDateTime(Date date) { if ( date != null ) { synchronized (SDF_DETAIL) { return SDF_DETAIL.format(date); } } else { return null; } }  static final void resetInternalDate(); static final String getYesterday(long currentTimeMillis); static final String getToday(long currentTimeMillis); static final String getWeek(long currentTimeMillis); static final String getLastMonth(long currentTimeMillis); static final String getCurrentMonth(long currentTimeMillis); static final int getSecondsToNextDateUnit(DateUnit dateUnit,
			Calendar currentTime); static final int getSecondsToTimeClock(long currentTimeMillis, String timeClock); static final long getMilliSecondsToNextDateUnit(DateUnit dateUnit,
			Calendar currentTime); static final String formatDate(Date date); static final String formatDateTime(Date date); static final String formatTime(Date date); static final Date parseApplePurchaseDate(String dateStr);  }### Answer:
@Test public void test() { Calendar cal = Calendar.getInstance(); cal.set(Calendar.HOUR_OF_DAY, 18); cal.set(Calendar.MINUTE, 0); cal.set(Calendar.SECOND, 0); System.out.println(DateUtil.formatDateTime(cal.getTime())); System.out.println(cal.getTimeInMillis()); }