Sample Functions to Parse Numbers and Strings into Dates (185732)

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When retrieving date values from legacy systems, the data may not be in a format supported by the CDate() function for converting other data types to date values. The functions below convert strings and numbers to date values based on a mask passed as an additional argument. The functions return NULL if an invalid mask is passed and a run-time error if a value is passed representing an invalid date.

   Num2Date converts a number to a date.

   String2Date converts a string to a date.

Masks supported by Num2Date:

   MMDDYY    MMDDYYYY
   DDMMYY    DDMMYYYY
   YYMMDD    YYYYMMDD

Masks supported by String2Date:

   MMDDYY    MMDDYYYY   MM/DD/YY   MM/DD/YYYY   M/D/Y   M/D/YY   M/D/YYYY
   DDMMYY    DDMMYYYY   DD/MM/YY   DD/MM/YYYY   DD-MMM-YY   DD-MMM-YYYY
   YYMMDD    YYYYMMDD   YY/MM/DD   YYYY/MM/DD

Example

Create a new VBA project and add a Module.

Add the following code to the module:

      Function Num2Date (ByVal N As Long, ByVal Fmt As String) As Variant
        Select Case Fmt
          Case "MMDDYY"             '052793
            Num2Date = CDate(N \ 10000 & "/" & N \ 100 Mod 100 & _
                             "/" & N Mod 100)
          Case "MMDDYYYY"           '05271993
            Num2Date = CDate(N \ 1000000 & "/" & N \ 10000 Mod 100 & _
                             "/" & N Mod 10000)
          Case "DDMMYY"             '270593
            Num2Date = CDate(N \ 100 Mod 100 & "/" & N \ 10000 & _
                             "/" & N Mod 100)
          Case "DDMMYYYY"           '27051993
            Num2Date = CDate(N \ 10000 Mod 100 & "/" & N \ 1000000 & _
                             "/" & N Mod 10000)
          Case "YYMMDD", "YYYYMMDD" '930527   19930527
            Num2Date = CDate(N \ 100 Mod 100 & "/" & N Mod 100 & "/" & _
                             N \ 10000)
          Case Else
            Num2Date = Null
        End Select
      End Function

      Function String2Date (ByVal S As String, _
                            ByVal Fmt As String) As Variant
        Select Case Fmt
          Case "MMDDYY", "MMDDYYYY"      '052793   05271993
            String2Date = CDate(Left(S, 2) & "/" & Mid(S, 3, 2) & "/" & _
                                Mid(S, 5))
          Case "DDMMYY", "DDMMYYYY"      '270593   27051993
            String2Date = CDate(Mid(S, 3, 2) & "/" & Left(S, 2) & "/" & _
                                Mid(S, 5))
          Case "YYMMDD"                  '930527
            String2Date = CDate(Mid(S, 3, 2) & "/" & Right(S, 2) & "/" & _
                                Left(S, 2))
          Case "YYYYMMDD"                '19930527
            String2Date = CDate(Mid(S, 5, 2) & "/" & Right(S, 2) & "/" & _
                                Left(S, 4))
          Case "MM/DD/YY", "MM/DD/YYYY", "M/D/Y", "M/D/YY", "M/D/YYYY", _
               "DD-MMM-YY", "DD-MMM-YYYY"
            String2Date = CDate(S)
          Case "DD/MM/YY", "DD/MM/YYYY"  '27/05/93   27/05/1993
            String2Date = CDate(Mid(S, 4, 3) & Left(S, 3) & Mid(S, 7))
          Case "YY/MM/DD"                '93/05/27
            String2Date = CDate(Mid(S, 4, 3) & Right(S, 2) & _
                                "/" & Left(S, 2))
          Case "YYYY/MM/DD"              '1993/05/27
            String2Date = CDate(Mid(S, 6, 3) & Right(S, 2) & _
                                "/" & Left(S, 4))
          Case Else
            String2Date = Null
        End Select
      End Function

Run the project and then pause it.

You can test the function in the Debug or Immediate window:


      ?Num2Date(19980203, "YYYYMMDD")
      #2/3/98#
      ?String2Date("020398", "MMDDYY")
      #2/3/98#

or in code:

Dim D1 As Date, D2 As Date
D1 = Num2Date(19980203, "YYYYMMDD")
D2 = String2Date("020398", "MMDDYY")

NOTE: As with any date conversion function, if only 2 digits of the year are supplied, you have the potential problem of distinguishing dates in the 1900s versus the 2000s. This can result in problems when calculating intervals for loan repayments, and so forth, when comparing two dates in different centuries. If only 2-digit years are supplied, the conversion functions adhere to the default "smart century" assumptions of the version of VBA that you are using. If you want to alter this behavior, you can easily modify the expressions for the appropriate masks.

Sample Functions to Parse Numbers and Strings into Dates (185732)

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