日期函数
=D4+E4/24/60
=(E9-D9)*60*24（再设置为常规模式）
=D14+E14
=E18-D18
=DATE(YEAR(B5),MONTH(B5)+C5,DAY(B5))
=DATE(YEAR(B13),MONTH(B13)+1,0)
=DATE(YEAR(B13),MONTH(B13)+1,1)-1
=DAY(DATE(YEAR(B13),MONTH(B13)+1,0))
=DATEDIF(B5,C5,"y")
=DATEDIF(B6,C6+1,"y")
=DATEDIF(B13,C13,"y")&"年"&DATEDIF(B13,C13,"ym")&"月"&DATEDIF(B13,C13,"md")&"天"
="第"&WEEKNUM(B13,2)&"周第"&WEEKDAY(B13,2)&"天"
=TEXT(B3,"aaaa")
=TEXT(B10,"0000-00-00")*1 （然后再转化为日期）