'功能：算出某个日期区间内星期天的个数
'作者：竹笛
'修改历史：2005/12/30
'未经严格测试，有问题请与作者交流

 

Function SundayCount(StartDate As Date, EndDate As Date) As Long
    On Error GoTo Err_SundayCount:
    Dim Days As Integer    '区间天数
    Dim FirstSunday As Date    '第一个周日具体日期
    Dim NextSunday As Date    '下一个周日具体日期
    Dim Myweekday As Integer
    Dim i As Long
    Dim j As Long
    '确保日期都不为空，若为空则置为0
    If Not IsNull(StartDate) And Not IsNull(EndDate) Then
    '如果结束日期<开始日期，则为0
        If EndDate >= StartDate Then
            '如果天数大于7,则先确定第一个周日是哪个日期，再7天一加，直到大于结束日期
            Days = EndDate - StartDate
            ' If Days > 7 Then
            Myweekday = Weekday(StartDate)    '算出是周几,星期天是1
            If Myweekday > 1 Then
                FirstSunday = StartDate + 8 - Myweekday
            Else
                FirstSunday = StartDate
            End If
            Debug.Print "最近的周日是: " & FirstSunday
            NextSunday = FirstSunday + 7
            i = 1
            SundayCount = 1
            For i = 1 To Days Step 7
                Debug.Print "下一个周日是: " & NextSunday
                If NextSunday > EndDate Then
                    If FirstSunday > EndDate Then
                        SundayCount = SundayCount - 1
                    End If
                    Debug.Print "周日数目是: " & SundayCount
                    Exit Function
                End If
                NextSunday = NextSunday + 7
                i = i + 1
                SundayCount = SundayCoun