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Date Verifier in VB

Posted on 2001-08-14
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Last Modified: 2010-08-05
In SQL there is a command ISDATE(YYMMDD) which returns 1 if the parameter is a date and 0 if it is not a valid date.  

I am looking for a built in Visual Basic function which will allow me to pass in a 6 character field and return either true or false depending on whether or not the string is a valid date.

Here are a few examples
"770705"  => True, This is July 5, 1977
"840010"  => False, there is no Month
"000101"  => True, This is January 1, 2000
"01B0pH"  => False, This is garbage data


If any one can tell me the VB equivalant to the SQL isdate command, I will reward them the points.  It is that simple...
Thanks


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Question by:ifgtest001
12 Comments
 
LVL 43

Expert Comment

by:TimCottee
ID: 6384039
There is an isdate function in VB. However it does require that there is some seperator in the expression to be evaluated so:

IsDate("770705") = False
IsDate("77-07-05") = True

But all is not lost, you can easily convert the 6 character string into an acceptable date format using:

IsDate(format("770705","yy-mm-dd")) = True
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LVL 6

Expert Comment

by:VK
ID: 6384054
try that:

exaple

isdate(format("980505","yy/dd/mm")) = true !
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LVL 43

Expert Comment

by:TimCottee
ID: 6384090
Beat you VK! It doesn't actually matter what the seperator is as long as it is a valid date seperator somewhere.
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Expert Comment

by:ture
ID: 6384447
Is this really correct??? I'm trying this in Excel VBA, but it really doesn't work the way you imply.

Please correct me if I'm wrong...

Try this in the immediate window:
?format("980505","yyyy/dd/mm")

It really doesn't show us the date 1998-05-05!
It shows us the date that is 980505 days from January 1 1900 - which is 4584-11-07.

To verify that "980505" is a date, you must insert separators and check if it's a date. This will work for a 6-digit YYMMDD date:

function isitadate(d as string) as boolean
  isitadate = isdate(mid(d,1,2) & "-" & mid(d,3,2) & "-" & mid(d,5,2))
end function

Ture Magnusson
Karlstad, Sweden
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Expert Comment

by:DennisBorg
ID: 6384517
>In SQL there is a command ISDATE(YYMMDD) which returns 1
>if the parameter is a date and 0 if it is not a valid date.

You might want to clarify which SQL environment you are speaking. The syntax, keywords, and functions differ from one DBMS to another. You don't do things exactly the same way in MS Access SQL as you do in MS SQL Server, or in Oracle SQL.

Ture is correct in the fact that the first couple of suggestions would return a date, but not the one you expected.

-Dennis Borg
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LVL 43

Expert Comment

by:TimCottee
ID: 6384547
I didn't actually test that the date determined was what it should have been, thanks ture for the extra mile.
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LVL 2

Expert Comment

by:AndrewK
ID: 6385016
... or the extra instruction: FormatDateTime(mydate, date_format) where date_format would be vbShortDate in the above examples.
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LVL 9

Expert Comment

by:Valliappan AN
ID: 6385326
Adding to previous comments, Try this:

Private Function CheckIfDate(MyDate As String)
Dim sDate As String

MyDate = "770705"

sDate = Left(MyDate,2) & "-" & Mid(MyDate,3,2) & "-" & Right(MyDate, 2)

CheckIfDate = IsDate(sDate)
End Sub

'Hope this helps.
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Expert Comment

by:ameba
ID: 6385626
? IsDate(Format("981005", "@@/@@/@@"))
True

' insert  /  characters
?Format("981005", "@@\/@@\/@@")
98/10/05

' insert date separators
?Format("981005", "@@/@@/@@")
98/10/05
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LVL 8

Expert Comment

by:DennisBorg
ID: 6385641
ifgtest001:

Here is an example illustrating how you can perform your check:


   IsDate(Format("770705","00/00/00"))

This will return either true or false

The only "thing" would be if you had dates such as the following:

   "010203"

Which should it be:

    Jan 02, 2003
    Feb 01, 2003
    Feb 03, 2001
    etc.

It is a little ambiguous, but doesn't change the fact of whether or not it is a valid date.


-Dennis Borg
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Expert Comment

by:DanRollins
ID: 7199948
Hi ifgtest001,
It appears that you have forgotten this question. I will ask Community Support to close it unless you finalize it within 7 days. I will ask a Community Support Moderator to:

    Save as PAQ -- No Refund.
    *** Too many excellent answers; too few points to split

ifgtest001, Please DO NOT accept this comment as an answer.
EXPERTS: Post a comment if you are certain that an expert deserves credit.  Explain why.
==========
DanRollins -- EE database cleanup volunteer
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Netminder earned 0 total points
ID: 7213439
Per recommendation, points NOT refunded and question closed.

Netminder
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