Microsoft KB Archive/184521

= IsDate Function Incorrectly Identifies Some Expressions =

Article ID: 184521

Article Last Modified on 10/10/2006

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APPLIES TO


 * Microsoft Excel 97 Standard Edition
 * Microsoft Excel 95 Standard Edition
 * Microsoft Excel 5.0 Standard Edition

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This article was previously published under Q184521





SYMPTOMS
In the programs that are listed at the beginning of this article, if you run a Visual Basic for Applications macro that uses the IsDate function to determine whether an expression can be converted into a date, the function may return the Boolean value True. This result is incorrect.



CAUSE
This problem occurs if the expression that is being evaluated by the IsDate function uses a date format that is not normally recognized as valid by Microsoft Excel. The following date formats are not recognized.   Format           Example -  year-day-month   2002, 5 July month-year-day  July, 2002 5 day-year-month  5, 2002 July Microsoft provides programming examples for illustration only, without warranty either expressed or implied. This includes, but is not limited to, the implied warranties of merchantability or fitness for a particular purpose. This article assumes that you are familiar with the programming language that is being demonstrated and with the tools that are used to create and to debug procedures. Microsoft support engineers can help explain the functionality of a particular procedure, but they will not modify these examples to provide added functionality or construct procedures to meet your specific requirements. For example, if you run the following macro Sub TestIsDateFunction MyDate = "2002, 5 July"  'an invalid date expression MsgBox IsDate(MyDate)    'is it a date? End Sub the message box displays True instead of False even though the date is not valid in Microsoft Excel.



RESOLUTION
If an expression uses a date format that includes a year, a month, and a day, in any order, the IsDate function returns True. There is no way to prevent this behavior.

However, you can use the CDate function to convert invalid expressions into valid dates, for example: Sub ConvertDate MyDate = "2002, 5 July"  'an invalid date expression CnDate = CDate(MyDate)   'convert MyDate into a valid date MsgBox CnDate            'display the new, valid date End Sub



STATUS
This behavior is by design of Visual Basic for Applications.



MORE INFORMATION
Depending on the regional settings that are in use on your computer, Microsoft Excel normally recognizes expressions that use any of the following formats as dates.   Format           Example -  month-day-year   July 5, 2002 day-month-year  5 July, 2002 year-month-day  2002, July 5 For example, if you enter July 5, 2002 into a cell, Microsoft Excel converts this expression into a proper date.

Expressions that use other formats (such as year-day-month) are not recognized as dates by Microsoft Excel. However, because of the design of the IsDate function, it returns True for any expression that contains a year, a month, and a day, in any order.

Additional query words: XL97 XL5 XL7 5.0 7.0 year2000 y2k year 2000 XL

Keywords: kbdtacode kbprb kbprogramming KB184521

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