Exclude Sat/Sun in Days Calculation

I have an Access dbase for order shipments set up with a table that includes the NeedByDate and ShipDate.  I need to calculate the number of days each shipment is early/late based on those 2 dates, but, I want to exclude Saturdays and Sundays in the calculation.  How can I accomplish this?
Example:  NeedByDate=4/7/00 and ShipDate=4/10/00, then shipment was only 1 day late, since sat/sun aren't included.
d_brownAsked:
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mgrattanConnect With a Mentor Commented:
Here is a function that will calculate the number of business days between each date provided.  In addition, it references a table that you can add to your database called "tblHolidays" where you can store the observed holidays for the year and have those taken into consideration as well.  If you don't need the additional functionality, just remove the section that searches for the holidays in the tblHolidays table and remove the parameter from the function.

Function DiffBusinessDays(datDay1 As Date, datDay2 As Date, strHolidayTbl As String, strHolidayField As String) As Long
  ' Comments  : Returns the number of business days between two dates
  '             The days are rounded down -- it takes 24 hours to make a day.
  '             Weekend dates (Saturday and Sunday) and holidays are not counted.
  ' Parameters: datDay1 - first (earlier) date/time (subtracted from datDay2)
  '             datDay2 - second (later) date/time
  '             strHolidayTbl - name of holiday table
  '             strHolidayField - field name of holiday dates in the holiday table
  ' Returns   : Number of whole business days between two dates
  '             (Returns negative days if datDay1 is after datDay2)
  '
  Dim db As Database
  Dim rst As Recordset
  Dim strSQL As String
  Dim strField As String
  Dim lngWeekdays As Long
  Dim lngBusinessDays As Long

  ' Calculate number of weekdays between two dates:
  lngWeekdays = DiffWeekdays(datDay1, datDay2)

  Set db = CurrentDb()
    strField = "[" & strHolidayTbl & "].[" & strHolidayField & "]"
    strSQL = "SELECT DISTINCTROW Count(" & strField & ") AS Count"
    strSQL = strSQL & " FROM [" & strHolidayTbl & "]"
    strSQL = strSQL & " WHERE ((" & strField

    If datDay1 <= datDay2 Then
      strSQL = strSQL & ">=#" & datDay1 & "# And "
      strSQL = strSQL & strField & "<#" & datDay2 & "#));"
    Else
      strSQL = strSQL & ">=#" & datDay2 & "# And "
      strSQL = strSQL & strField & "<#" & datDay1 & "#));"
    End If

    Set rst = db.OpenRecordset(strSQL)
      lngBusinessDays = rst![Count]
    rst.Close
  db.Close

  DiffBusinessDays = lngWeekdays - lngBusinessDays

End Function
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francois_dionCommented:
Although I can't think of a way to do it directly with Access' function, it isn't difficult to whip up a little something to do this...

Public Function WorkDaysLate(NeedByDate As Date, ShipDate As Date) As Long
    Dim lDiff As Long
    Dim dtmSkipper As Date
   
    lDiff = 0
    If (VarType(NeedByDate) = vbDate And VarType(ShipDate) = vbDate) Then
        If NeedByDate < ShipDate Then
            For dtmSkipper = NeedByDate + 1 To ShipDate
                If WeekDay(dtmSkipper) <> vbSunday And _
                    WeekDay(dtmSkipper) <> vbSaturday Then _
                    lDiff = lDiff + 1
            Next
        End If
    End If

    WorkDaysLate = lDiff
End Function

This little function simply skips through the days, checks if they're not sundays or saturdays to return the number of days late, or a flat zero if the dates don't indicate lateness...

>:) If you need to set it into a query, just send the column names of the select query into the function, easy as pie.
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francois_dionCommented:
Although I can't think of a way to do it directly with Access' function, it isn't difficult to whip up a little something to do this...

Public Function WorkDaysLate(NeedByDate As Date, ShipDate As Date) As Long
    Dim lDiff As Long
    Dim dtmSkipper As Date
   
    lDiff = 0
    If (VarType(NeedByDate) = vbDate And VarType(ShipDate) = vbDate) Then
        If NeedByDate < ShipDate Then
            For dtmSkipper = NeedByDate + 1 To ShipDate
                If WeekDay(dtmSkipper) <> vbSunday And _
                    WeekDay(dtmSkipper) <> vbSaturday Then _
                    lDiff = lDiff + 1
            Next
        End If
    End If

    WorkDaysLate = lDiff
End Function

This little function simply skips through the days, checks if they're not sundays or saturdays to return the number of days late, or a flat zero if the dates don't indicate lateness...

>:) If you need to set it into a query, just send the column names of the select query into the function, easy as pie.
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mgrattanCommented:
Addition to my comment:

You will need this function as well in order for the previously mentioned function to work correctly:

Function DiffWeekdays(datDay1 As Date, datDay2 As Date) As Long
  ' Comments  : Returns the number of weekdays between two dates
  '             The days are rounded down -- it takes 24 hours to make a day.
  ' Parameters: datDay1 - first (earlier) date/time (subtracted from datDay2)
  '             datDay2 - second (later) date/time
  ' Returns   : Number of whole business days between two dates
  '             (Returns negative days if datDay1 is after datDay2)
  '
  Dim lngDays As Long
  Dim lngWeeks As Long
  Dim datFirstDate As Date
  Dim datLastDate As Date
  Dim datNewDate As Date
  Dim intDirection As Integer

  If datDay1 < datDay2 Then
    datFirstDate = datDay1
    datLastDate = datDay2
    intDirection = 1
  Else
    datFirstDate = datDay2
    datLastDate = datDay1
    intDirection = -1
  End If
 
  ' Subtract weekends
  lngWeeks = Fix(Fix(datLastDate - datFirstDate) / 7)
  lngDays = lngWeeks * 5

  datNewDate = CDate(datFirstDate) + lngWeeks * 7

  While datNewDate < datLastDate
    datNewDate = datNewDate + 1
    If datNewDate <= datLastDate Then

      ' Don't count days when new day is Sunday or Monday.
      ' (When new day is Saturday, you are actually counting Friday)
      If WeekDay(datNewDate) <> 1 And WeekDay(datNewDate) <> 2 Then
        lngDays = lngDays + 1
      End If

    End If
  Wend

  DiffWeekdays = intDirection * lngDays

End Function
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hnasrCommented:
' here is a try:

' you need to have a table called tblRestarts_weekends: the name was used to answer another EE question.  You can replace with ur own table.
' one field,  weekenddate as date/time : short date

' you need a function to count the number of sats/sundays

' button, dates passed from text fields, or any other way.
' to calculate the number of saturdays/sundays between dateFrom and dateTo

Private Sub count_weekeends_Click()
    Dim no_of_weekend_days As Integer
    no_of_weekend_days = count_weekends(Me!NeedByDate, Me!ShipDate)
End Sub

' here is the function: count_weekends(Me!dateFrom, Me!DateTo)
' in a module

Public Function count_weekends(dateFrom As Variant, DateTo As Variant) As Variant
    Dim db As Database
    Dim rs As Recordset
    Dim x As Variant
    Dim aDate As Variant
    Set db = CurrentDb
   
    count_weekends = 0
    aDate = dateFrom
    Do While aDate < DateTo
        x = WeekDay(aDate)
        If x = 1 Or x = 7 Then
            count_weekends = count_weekends + 1
        Else
        End If
        aDate = DateAdd("d", 1, aDate)
    Loop
End Function

' You can find the no of days late as:

no_of_days_late = DateDiff ("d", NeedByDate, ShipDate) - no_of_weekend_days

' ----
'Using a query: here are the querey fields:

 NeedByDate            ShipDate           days_late: DateDiff("d", [NeedByDate], [ShipDate]) - count_weekends([NeedByDate], [ShipDate])
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d_brownAuthor Commented:
Actually I had found some code elsewhere, and finally got it working right about the time I got your answer.  It is basically the same as your suggestion.  Thank you for your help and quick response!
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mgrattanCommented:
No problem!
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