Option Explicit

Function vbaThirdFriday(ByVal aDate As Date) As Date
   On Error GoTo ErrorLabel
   Dim Roll As Date
   Roll = DateSerial(Year(aDate), Month(aDate), 15)
   vbaThirdFriday = Roll + (13 - WeekDay(Roll)) Mod 7
Exit Function
ErrorLabel:
   MsgBox "error in vbaThirdFriday( " + str(aDate) + " )"
   vbaThirdFriday = aDate
End Function

Function vbaThirdFridayQuarter(ByVal aDate As Date) As Date
   On Error GoTo ErrorLabel
   Dim Roll As Date
   Dim Quarter As Integer
   Quarter = 1 + 3 * ((Month(aDate) - 1) \ 3)
   Roll = DateSerial(Year(aDate), Quarter, 15)
   vbaThirdFridayQuarter = Roll + (13 - WeekDay(Roll)) Mod 7
Exit Function
ErrorLabel:
   MsgBox "error in vbaThirdFridayQuarter( " + str(aDate) + " )"
   vbaThirdFridayQuarter = aDate
End Function

Function vbaThirdFridayYearly(ByVal aDate As Date) As Date
   On Error GoTo ErrorLabel
   Dim Roll As Date
   Roll = DateSerial(Year(aDate), 1, 15)
   vbaThirdFridayYearly = Roll + (13 - WeekDay(Roll)) Mod 7
Exit Function
ErrorLabel:
   MsgBox "error in vbaThirdFridayYearly( " + str(aDate) + " )"
   vbaThirdFridayYearly = aDate
End Function

Function vbaNextSettlement(ByVal aDate As Date) As Date
   On Error GoTo ErrorLabel
   vbaNextSettlement = vbaThirdFriday(aDate)
   If vbaNextSettlement <= aDate Then
      vbaNextSettlement = vbaThirdFriday(vbaNextSettlement + 20)
   End If
Exit Function
ErrorLabel:
   MsgBox "error in vbaNextSettlement( " + str(aDate) + " )"
   vbaNextSettlement = aDate
End Function

Function vbaNextSettlementQuarterly(ByVal aDate As Date) As Date
   On Error GoTo ErrorLabel
   vbaNextSettlementQuarterly = vbaThirdFridayQuarter(aDate)
   If vbaNextSettlementQuarterly <= aDate Then
      vbaNextSettlementQuarterly = vbaThirdFridayQuarter(vbaNextSettlementQuarterly + 90)
   End If
Exit Function
ErrorLabel:
   MsgBox "error in vbaNextSettlementQuarterly( " + str(aDate) + " )"
   vbaNextSettlementQuarterly = aDate
End Function

Function vbaNextSettlementyearly(ByVal aDate As Date) As Date
   On Error GoTo ErrorLabel
   ' find third friday in this month
   vbaNextSettlementyearly = vbaThirdFridayYearly(aDate)
   If vbaNextSettlementyearly <= aDate Then
      vbaNextSettlementyearly = vbaThirdFridayYearly(vbaNextSettlementyearly + 355)
   End If
Exit Function
ErrorLabel:
   MsgBox "error in vbaNextSettlementyearly( " + str(aDate) + " )"
   vbaNextSettlementyearly = aDate
End Function

Function vbaPrevSettlement(ByVal aDate As Date) As Date
   On Error GoTo ErrorLabel
   vbaPrevSettlement = vbaThirdFriday(aDate)
   If vbaPrevSettlement > aDate Then
      vbaPrevSettlement = vbaThirdFriday(vbaPrevSettlement - 30)
   End If
Exit Function
ErrorLabel:
   MsgBox "error in vbaPrevSettlement( " + str(aDate) + " )"
   vbaPrevSettlement = aDate
End Function

Function vbaPrevSettlementQuarterly(ByVal aDate As Date) As Date
   On Error GoTo ErrorLabel
   vbaPrevSettlementQuarterly = vbaThirdFridayQuarter(aDate)
   If vbaPrevSettlementQuarterly > aDate Then
      vbaPrevSettlementQuarterly = vbaThirdFridayQuarter(vbaPrevSettlementQuarterly - 30)
   End If
Exit Function
ErrorLabel:
   MsgBox "error in vbaPrevSettlementQuarter( " + str(aDate) + " )"
   vbaPrevSettlementQuarterly = aDate
End Function

Function vbaPrevSettlementYearly(ByVal aDate As Date) As Date
   On Error GoTo ErrorLabel
   vbaPrevSettlementYearly = vbaThirdFridayYearly(aDate)
   If vbaPrevSettlementYearly > aDate Then
      vbaPrevSettlementYearly = vbaThirdFridayYearly(vbaPrevSettlementYearly - 355)
   End If
Exit Function
ErrorLabel:
   MsgBox "error in vbaPrevSettlementyearly( " + str(aDate) + " )"
   vbaPrevSettlementYearly = aDate
End Function