Q190471: BUG: CTime::Format Returns Wrong Date If the Date Field Is NULL

Article: Q190471
Product(s): Microsoft C Compiler
Version(s): 5.0,6.0
Operating System(s): 
Keyword(s): kbVC600bug
Last Modified: 07-FEB-2002

-------------------------------------------------------------------------------
The information in this article applies to:

- Microsoft Visual C++, 32-bit Enterprise Edition, versions 5.0, 6.0 
- Microsoft Visual C++, 32-bit Professional Edition, versions 5.0, 6.0 
- Microsoft Visual C++, 32-bit Learning Edition, version 6.0 
- Microsoft Visual C++.NET (2002) 
-------------------------------------------------------------------------------

SYMPTOMS
========

The string 01/01/1970 or its equivalent, depending on the time zone, is returned
by CTime::Format() when the CTime object is NULL. It is expected to return a
blank string when the CTime object is NULL.

CAUSE
=====

CTime only measures dates after 12:00 a.m. 01/01/1970 GMT.

CTime::Format() makes a call to localtime(), which is expected to return a blank
string when the date is null or invalid. Instead, it returns the date 12:00 a.m.
01/01/1970 GMT sufficiently compensated with respect to the time zone settings
of the computer.

For example, if the time zone is set to Eastern (US and Canada only), then the
date returned is 12/31/69 because it is 5 hours behind GMT.

RESOLUTION
==========

Insert an "If condition" to check whether the CTime object is NULL. If it is,
then do not make a call to CTime::Format(). For example:

     CTime newVar;
     // Other code to manipulate CTime
     if (newVar == NULL)
       cout << "Date: 'Date is Blank'" << endl;
     else
       cout << "Date:" << newVar.Format("%m/%d/%y")<<endl;
     // Remaining code

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article. We are researching this bug and will post new
information here in the Microsoft Knowledge Base as it becomes available.

MORE INFORMATION
================

Steps to Reproduce Behavior
---------------------------

1. Create a Win32 Console Application.

2. Type in the following sample code:

        #include <iostream.h>
        #include <afx.h>
        int main(void)
        {
           CTime newVar = NULL;
           cout<< "CTime::Format():" << newVar.Format("%m/%d/%y") << endl;
           return 0;
        }

3. On the Project menu, click Settings, click the General tab and select Use
  MFC.

4. The output for Eastern Time zone (US and Canada only) can be viewed as
  12/31/69.

Additional query words: kbvc500bug kbVC600bug kbDatabase kbMFC

======================================================================
Keywords          : kbVC600bug 
Technology        : kbVCsearch kbAudDeveloper kbVC500 kbVC600 kbVC32bitSearch kbVCNET kbVC500Search
Version           : :5.0,6.0
Issue type        : kbbug
Solution Type     : kbpending

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.

Copyright Microsoft Corporation 1986-2002.