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How to Normalise the date? (Converting user-defined dates into meaningful date)

Posted on 2004-10-12
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Last Modified: 2013-12-26
How do I convert (normalise) the user-defined dates into meaningful dates?  
For example:  If the user enters date '29-Feb-2002' must return '1-Mar-2002' (29th Feb is not a valid date and hence the next day is returned).  

Similarly, if the user enters '31-30-2000' must return '1-Jul-2003' (As the months 30 is invalid, it must return 30 months from the year 2000 which results June, 2003 but the date is 31st and there is no 31st in June, it must return the next day i.e. 1-Jul-2003).

Also, I must be able to set my own default date for date calculation.  For example: If I set Default Date as '01-01-2004' and I pass a date i.e. '10-10-2004', it must return the No. of days from 1st Jan, 2004 which is 284 days and if the user enters 284 days, it must return '10-10-2004'.

The User can enter either '01/01/2004' or '01-Jan-2004' or '01-January-2004' formats.  How do I validate the date string?

Thank you Experts in advance.
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Question by:kvnagaraj2000
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by:gary_j
gary_j earned 250 total points
ID: 12286847
[Also, I must be able to set my own default date for date calculation.  For example: If I set Default Date as '01-01-2004' and I pass a date i.e. '10-10-2004', it must return the No. of days from 1st Jan, 2004 which is 284 days and if the user enters 284 days, it must return '10-10-2004']

numDays = dateDiff("d",date1,date2)

newdate = dateadd("d",numDays,date)

As to the rest of your problem, I think you're going to have to write a comprehensive parsing routine or have some rules -- one or the other.  If it is "freestyle" entry, things like the cdate function just are not reliable.
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by:fds_fatboy
ID: 12287359
To validate the dates use IsDate - but beware of it as it does this: First it attempts to validate the date in the user's locale, if it fails it will swap the day and month and try again. I have a better conversion routine which I use in my calendar control. I will try and dig it out.

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by:gary_j
ID: 12287415
the problem with isdate is that it will completely fail on things like ('31-30-2000').  
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fds_fatboy earned 250 total points
ID: 12287637
Here it is I have attempted to get the relevant bits: - in fact, I will comment out the bits that are not relevant for you. If you reinstate the commented out parts, all invalid dates will return error 5, otherwise it will let 29 feb 2001 etc through returning 1 Mar 2001 etc.

Private MstrDateSeparator As String 'Elsewhere set to "/"
Private Const McstrValidSeparators As String = "/. ,~_-"

Public Enum DateEntryOrder
'    [Default VB date] = 0 ' Your locale setting
    [Day/Month/Year]
    [Month/Day/Year]
    [Year/Month/Day]
End Enum

Private Function Text2Date(PstrText As String, Optional PlngEntryOrder As DateEntryOrder = [Default VB date]) As Date
    Dim LlngIndex As Long
    Dim LstrDatepart() As String
    Dim LdteDate As Date

    On Error GoTo ErrorHandler

    For LlngIndex = 1 To Len(PstrText)
        If Mid$(PstrText, LlngIndex, 1) Like "[" & McstrValidSeparators & "]" Then
            Mid$(PstrText, LlngIndex, 1) = MstrDateSeparator
        End If
    Next

    LstrDatepart = Split(PstrText, MstrDateSeparator)

    Select Case PlngEntryOrder
'    Case DateEntryOrder.[Default VB date]
'        Text2Date = CDate(PstrText)
    Case DateEntryOrder.[Day/Month/Year]
        If Not IsNumeric(LstrDatepart(1)) Then
            LstrDatepart(1) = DatePart("m", "13 " & LstrDatepart(1) & " 2000")
        End If

        LdteDate = DateSerial(CInt(LstrDatepart(2)), CInt(LstrDatepart(1)), CInt(LstrDatepart(0)))

'        If CInt(DatePart("d", LdteDate)) = CInt(LstrDatepart(0)) And _
'           CInt(DatePart("m", LdteDate)) = CInt(LstrDatepart(1)) And _
'           CInt(DatePart("yyyy", LdteDate)) = CInt(LstrDatepart(2)) Then
           Text2Date = LdteDate
'        Else
'            Err.Raise 5
'        End If

    Case DateEntryOrder.[Month/Day/Year]
        If Not IsNumeric(LstrDatepart(0)) Then
            LstrDatepart(0) = DatePart("m", "13 " & LstrDatepart(0) & " 2000")
        End If

        LdteDate = DateSerial(CInt(LstrDatepart(2)), CInt(LstrDatepart(0)), CInt(LstrDatepart(1)))

 '       If CInt(DatePart("d", LdteDate)) = CInt(LstrDatepart(1)) And _
 '          CInt(DatePart("m", LdteDate)) = CInt(LstrDatepart(0)) And _
 '          CInt(DatePart("yyyy", LdteDate)) = CInt(LstrDatepart(2)) Then
           Text2Date = LdteDate
 '       Else
 '           Err.Raise 5
 '       End If

    Case DateEntryOrder.[Year/Month/Day]
        If Not IsNumeric(LstrDatepart(1)) Then
            LstrDatepart(1) = DatePart("m", "13 " & LstrDatepart(1) & " 2000")
        End If

        LdteDate = DateSerial(CInt(LstrDatepart(0)), CInt(LstrDatepart(1)), CInt(LstrDatepart(2)))

 '       If CInt(DatePart("d", LdteDate)) = CInt(LstrDatepart(2)) And _
 '          CInt(DatePart("m", LdteDate)) = CInt(LstrDatepart(1)) And _
 '          CInt(DatePart("yyyy", LdteDate)) = CInt(LstrDatepart(0)) Then
           Text2Date = LdteDate
 '       Else
 '           Err.Raise 5
 '       End If

    Case Else
        Err.Raise 5
    End Select

    Exit Function
ErrorHandler:
    With Err
         .Raise .Number, .Source, .Description, .HelpFile, .HelpContext
    End With

End Function
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Expert Comment

by:fds_fatboy
ID: 12287692
gary_j:

Yes - and IsDate is crap. e.g. A user's locale says dates are in dd/mm/yyyy format and they type in 12/31/2004, Is date says it's ok.
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by:fds_fatboy
ID: 12287821
My earlier example distilled for this problem:

Private Const McstrValidSeparators As String = "/. ,~_-"

Private Function Text2Date(ByVal PstrText As String) As Date
    Dim LlngIndex As Long
    Dim LstrDatepart() As String

    On Error GoTo ErrorHandler

    PstrText = Trim$(PstrText)

    If PstrText = vbNullString then
        Err.Raise 5
    End If

    For LlngIndex = 1 To Len(PstrText)
        If Mid$(PstrText, LlngIndex, 1) Like "[" & McstrValidSeparators & "]" Then
            Mid$(PstrText, LlngIndex, 1) = "/"
        End If
    Next

    LstrDatepart = Split(PstrText, MstrDateSeparator)

    If UBound(LstrDatepart) <> 2 Then
        Err.Raise 5
    End If

    If Not IsNumeric(LstrDatepart(1)) Then
        LstrDatepart(1) = DatePart("m", "13 " & LstrDatepart(1) & " 2000")
    End If

   'in this case entry is d/m/y - LstrDatePart (0) is Day; (1) is Month; (2) is Year  
   Text2Date = DateSerial(CInt(LstrDatepart(2)), CInt(LstrDatepart(1)), CInt(LstrDatepart(0)))
    Exit Function
ErrorHandler:
    With Err
         .Raise .Number, .Source, .Description, .HelpFile, .HelpContext
    End With

End Function
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by:fds_fatboy
ID: 12814469
points split Gary_j/fds_fatboy?
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