code: public static Calendar beginOfQuarter(Calendar calendar) {
  		calendar.set(Calendar.MONTH, calendar.get(DateField.MONTH.getValue()) / 3 * 3);
  		calendar.set(Calendar.DAY_OF_MONTH, 1);
  		return beginOfDay(calendar);
  	}
docs: 获取某季度的开始时间
  
  @param calendar 日期 {@link Calendar}
  @return {@link Calendar}
  @since 4.1.0