DateTimePicker1.Date:=StartOfTheYear(Now)；//今年第一天的日期

DateTimePicker2.Date:=EndOfTheYear(Now);    //今年最后一天的日期

DateTimePicker3.Date:=StartOfTheMonth(Now)；//本月第一天的日期

DateTimePicker4.Date:=EndOfTheMonth(Now);    //本月最后一天的日期

DateTimePicker5.Date:=StartOfTheWeek(Now);   //本周第一天的日期

DateTimePicker5.Date:=EndOfTheWeek(Now);   //本周最后一天的日期