format the date before you do your calculations. I found the following function that acts as a format function for dates, pass in the date and the format you want it in and it returns it to you in that format:
(I take it this is not being done in VB as VB has its won Format function)
Function fnFormatDate(dtDate, strFormat)
' the VBScript function FormatDateTime depends on system settings,
' we want to be independent from that and emulate the VB Format Function
' dtDate = the date for format
' strFormat = the format as in the VB Format function
' returns as string with the formatted date
On Error Resume Next
'on error goto 0
'err.clear
Dim arMonths, strTheDate
If Not IsDate(dtDate) Then
strTheDate = "invalid date"
Else
strTheDate = strFormat
If Instr(strTheDate,"dd"

Then
If Day(dtDate) > 9 Then
strTheDate = Replace(strTheDate,"dd",cstr(Day(dtDate)))
Else
strTheDate = Replace(strTheDate,"dd","0" & cstr(Day(dtDate)))
End If
End If
If Instr(strTheDate,"d"

Then
strTheDate = Replace(strTheDate,"d",cstr(Day(dtDate)))
End If
If Instr(strTheDate,"mmmm"

Then
arMonths = Array("January","February","March","April","May","June","July","August","September","October","November","December"

strTheDate = Replace(strTheDate,"mmmm",cstr(arMonths(Month(dtDate)-1)))
ElseIf Instr(strTheDate,"mmm"

Then
arMonths = Array("Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sep","Oct","Nov","Dec"

strTheDate = Replace(strTheDate,"mmm",cstr(arMonths(Month(dtDate)-1)))
ElseIf Instr(strTheDate,"mm"

Then
'strTheDate = Replace(strTheDate,"mm",cstr(Month(dtDate)))
If Month(dtDate) > 9 Then
strTheDate = Replace(strTheDate,"mm",cstr(Month(dtDate)))
Else
strTheDate = Replace(strTheDate,"mm","0" & cstr(Month(dtDate)))
End If
ElseIf Instr(strTheDate,"m"

Then
' If Month(dtDate) > 9 Then
strTheDate = Replace(strTheDate,"m",cstr(Month(dtDate)))
' Else
' strTheDate = Replace(strTheDate,"m","0" & cstr(Month(dtDate)))
' End If
End If
If Instr(strTheDate,"yyyy"

Then
strTheDate = Replace(strTheDate,"yyyy",cstr(Year(dtDate)))
ElseIf Instr(strTheDate,"yy"

Then
strTheDate = Replace(strTheDate,"yy",Right(cstr(Year(dtDate)),2))
End If
End If
' return the string
If Err.number = 0 Then
fnFormatDate = strTheDate
Else
fnFormatDate = Err.description
Err.Clear
End If
End Function