year(serial_num) [返回日期serial_num的年份值]
month(serial_num) [返回日期serial_num的月份值]
weekday(serial_num,[return_type]) [返回日期serial_num的是周几]
weeknum(serial_num) [返回日期serial_num的在这一年的第几周]
day(serial_num) [返回日期serial_numde是哪号]
date
now [返回现在的时间]
today [返回现在的日期]
注：serial_num格式为XXXX/XX/XX/才可以识别
