code: public static boolean isSameDay(Calendar cal1, Calendar cal2) {
  		if (cal1 == null || cal2 == null) {
  			throw new IllegalArgumentException("The date must not be null");
  		}
  		return cal1.get(Calendar.DAY_OF_YEAR) == cal2.get(Calendar.DAY_OF_YEAR) && //
  				cal1.get(Calendar.YEAR) == cal2.get(Calendar.YEAR) && //
  				cal1.get(Calendar.ERA) == cal2.get(Calendar.ERA);
  	}
docs: 比较两个日期是否为同一天
  
  @param cal1 日期1
  @param cal2 日期2
  @return 是否为同一天
  @since 4.1.13