日期计算

 '周
        Dim intWeekDay As Integer
        Dim stDay As DateTime   '本周第一天   
        Dim PstDay As DateTime   '上周第一天   
        intWeekDay = DatePart(DateInterval.Weekday, Today)   '取得今天是星期几   
        stDay = DateAdd(DateInterval.Day, -1 * intWeekDay + 1, Today)   '计算本周第一天的日期   
        PstDay = DateAdd(DateInterval.Day, 7 + 1 - 2, stDay)   '计算本周最后一天的日期    
        Me.DataGridView1.DataSource = caxun(stDay, PstDay, "all", 0).Tables("log")

        '月
        Dim intMonthDay As Integer
        Dim stDay As DateTime   '本月第一天   
        Dim PstDay As DateTime   '上月第一天   
        intMonthDay = DatePart(DateInterval.Day, Today)   '取得今天是本月第几天  
        stDay = DateAdd(DateInterval.Day, -1 * intMonthDay + 1, Today)   '计算本月第一天的日期   
        PstDay = DateAdd(DateInterval.Day, DateTime.DaysInMonth(Today.Year, Today.Month) - 1, stDay)   '计算本月最后一天的日期   
        Me.DataGridView1.DataSource = caxun(stDay, PstDay, "in", 0).Tables("log")

        '年
        Dim intMonthDay As Integer
        Dim stDay As DateTime   '本年第一天   
        Dim PstDay As DateTime   '上年第一天   
        intMonthDay = DatePart(DateInterval.DayOfYear, Today)   '取得今天是本年第几天  
        stDay = DateTime.Parse(Today.Year & "-01-01") '计算本年第一天的日期  
        PstDay = DateTime.Parse(Today.Year & "-12-31") '计算本年最后一天的日期