[AccessD] Date difference

Hi Ray

As a supplement to Arthur's comments here's a function we use for
calculating workhours. It might help you.

<code>

Public Function ISO_WorkTimeDiff(ByVal datDateTimeFrom As Date, _
                                 ByVal datDateTimeTo As Date, _
                                 Optional ByVal booNoHours As Boolean) As Long

' Purpose: Calculate number of working minutes between date/times datDateTimeFrom and datDateTimeTo.
' Assumes: 5 or 6 working days per week. Weekend is (Saturday and) Sunday.
' Returns: "Working minutes". Divide by 60 to obtain working hours.
' Limitation: Does not count for public holidays.
'
' May be freely used and distributed.
' 2001-06-26. Gustav Brock, Cactus Data ApS, Copenhagen
'
' If booNoHours is True, time values are ignored.

  ' Specify begin and end time of daily working hours.
  Const cdatWorkTimeStart   As Date = #8:00:00 AM#
  Const cdatWorkTimeStop    As Date = #4:00:00 PM#
  Const cbytWorkdaysOfWeek  As Byte = 5

  Dim bytSunday             As Byte
  Dim intWeekdayDateFrom    As Integer
  Dim intWeekdayDateTo      As Integer
  Dim datTimeFrom           As Date
  Dim datTimeTo             As Date
  Dim lngDays               As Long
  Dim lngMinutes            As Long
  Dim lngWorkMinutesDaily   As Long
  
  ' No special error handling.
  On Error Resume Next
  
  If DateDiff("n", datDateTimeFrom, datDateTimeTo) <= 0 Then
    ' Nothing to do. Return zero.
  Else
    
    ' Calculate number of daily "working minutes".
    lngWorkMinutesDaily = DateDiff("n", cdatWorkTimeStart, cdatWorkTimeStop)
    
    ' Find ISO weekday for Sunday.
    bytSunday = WeekDay(vbSunday, vbMonday)
    
    ' Find weekdays for the dates.
    intWeekdayDateFrom = WeekDay(datDateTimeFrom, vbMonday)
    intWeekdayDateTo = WeekDay(datDateTimeTo, vbMonday)
    
    ' Compensate weekdays' value for non-working days (weekends).
    intWeekdayDateFrom = intWeekdayDateFrom + (intWeekdayDateFrom = bytSunday)
    intWeekdayDateTo = intWeekdayDateTo + (intWeekdayDateTo = bytSunday)
    
    ' Calculate number of working days between the weeks of the two dates.
    lngDays = (cbytWorkdaysOfWeek * DateDiff("w", datDateTimeFrom, datDateTimeTo, vbMonday, vbFirstFourDays))
    ' Add number of working days between the two weekdays, ignoring number of weeks.
    lngDays = lngDays + intWeekdayDateTo - intWeekdayDateFrom - (cbytWorkdaysOfWeek * (intWeekdayDateTo < intWeekdayDateFrom))
    
    If Not booNoHours = True Then
      ' Extract begin and stop hour (time) for the working period.
      datTimeFrom = TimeSerial(Hour(datDateTimeFrom), Minute(datDateTimeFrom), Second(datDateTimeFrom))
      datTimeTo = TimeSerial(Hour(datDateTimeTo), Minute(datDateTimeTo), Second(datDateTimeTo))
      ' Adjust times before or after daily working hours to boundaries of working hours.
      If DateDiff("n", datTimeFrom, cdatWorkTimeStart) > 0 Then
        datTimeFrom = cdatWorkTimeStart
      ElseIf DateDiff("n", datTimeFrom, cdatWorkTimeStop) < 0 Then
        datTimeFrom = cdatWorkTimeStop
      End If
      If DateDiff("n", datTimeTo, cdatWorkTimeStart) > 0 Then
        datTimeTo = cdatWorkTimeStart
      ElseIf DateDiff("n", datTimeTo, cdatWorkTimeStop) < 0 Then
        datTimeTo = cdatWorkTimeStop
      End If
      
      ' Calculate number of working minutes between the two days, ignoring number of days.
      lngMinutes = DateDiff("n", datTimeFrom, datTimeTo)
    End If
    
    ' Calculate number of working minutes between the two days using the workday count.
    lngMinutes = lngMinutes + (lngDays * lngWorkMinutesDaily)
  
  End If
  
  ISO_WorkTimeDiff = lngMinutes

End Function

</code>

Beware of line breaks.

/gustav