KB190471 - CTime::Format() returns a wrong date if the CTime object is NULL when the time zone is set to Eastern (US and Canada only) in Visual C++ .NET

Article ID: 190471

Article Last Modified on 1/11/2006

Microsoft Visual C++ 5.0 Enterprise Edition
Microsoft Visual C++ 6.0 Enterprise Edition
Microsoft Visual C++ 5.0 Professional Edition
Microsoft Visual C++ 6.0 Professional Edition
Microsoft Visual C++ 6.0 Standard Edition
Microsoft Visual C++ .NET 2003 Standard Edition
Microsoft Visual C++ .NET 2002 Standard Edition

This article was previously published under Q190471

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 that this is a bug in the Microsoft products that are listed in the "Applies to" section. 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 the behavior

Create a Win32 Console Application.

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;
      }

On the Project menu, click Settings, click the General tab and select Use MFC.
The output for Eastern Time zone (US and Canada only) can be viewed as 12/31/69.

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