| Microsoft Year 2000 Readiness Disclosure
& Resource Center |
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| C Runtime Libraries and the Year 2038
Issue |
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What is the
Year 2038 issue?
To ensure that software programs can communicate with other
applications and with hardware on different machines from multiple
vendors, software developers write programs according to industry
standards.
The root of the year 2038 issue is an industry-standard data type
that can only represent dates between 1/1/1970 and 1/18/2038. It is
the American National Standards Institute (ANSI) data type known as
time_t.
After January 18, 2038, applications that rely on the 32-bit
ANSI C time_t data type may not function as expected.
In software programming languages, the data type indicates
what sort of value a data object (variable) represents, such as
whether it is a floating-point number (one that can contain a
fractional part), a character (text), or an integer (whole number).
The ANSI C time_t data type is a signed integer that is
stored in 32 bits. The first of these bits is used to represent the
sign (for a positive or negative number); the remaining 31 bits are
used to store the number of seconds elapsed since January 1, 1970 at
12:00:00 AM GMT.
The maximum number of seconds that can be stored in the time_t
value is 2147483647 (that's a little over 68 years). Once a signed
integer has reached its maximum value, it wraps around to its lowest
possible negative value the next time it is incremented. So
at 8 seconds past 3:14 AM on January 19, 2038 the time_t value will
wrap around to û2147483648. This represents December 13, 1901 at
8:45:52 PM GMT.
Most, if not all, C applications use 1970 as the reference date
and will overflow in 2038. Overflow means that the 31 bits
used to hold the numeric representation of the integer can no longer
represent the value. This overflow may cause an application to post
error messages or reset the date counter to January 1, 1970.
Programs are composed of one or more independently developed
modules; each module contains one or more functions. A
function is a named section of a program that performs a
specific task. The C and C++ programming languages come with a
prewritten set of functions (also called routines). This collection
of precompiled functions is called a library.
The C and C++ languages rely on library routines for input-output
and other interactions with the computer. The Microsoft Visual C
Runtime (MSVCRT) library includes several functions that use
parameters of time_t. For example: time, ctime, difftime, gmtime,
localtime, mktime, and utime.
Most of the support functions that use the time_t data
type cannot handle negative values. Also, many of them (for
example functions that call for printing or display) may not return
an error code. So after January 18, 2038 applications that rely on
time_t may not function as expected.
How is time_t related to the "operational range" listed
in Microsoft Year 2000 compliance documents?
Time structures in software programs affect a product's
operational range. The time_t function is only one of many time
structures that can be used in programs.
Microsoft products have a variety of operational date ranges as a
result of a number of interoperability/compatibility date
structures. The operational range of a product indicates the
limits within which the product behaves as functionally intended.
Outside these limits the product may or may not continue to function
normally, depending on the specific functions being used.
The date handling methods within a software product are tailored
to the needed functionality. Various methods (algorithms) can be
used depending on the functions required, so each method may extend
normal functionality to a different date limit. Examples of various
date functionality include valid data ranges the product will
accept, valid dates for the file itself, and the date ranges within
which the product will initialize.
When programmers use Microsoft development tools, they can choose
which application program interfaces (APIs) to include, and some of
them have used the C/C++ runtime APIs designed to manipulate time_t
values. Custom-coded date handling routines also can be a factor in
determining a product's operational range. Developers have continued
to include time_t in their applications because it is a convenient
way to handle dates and times in C and C++ programs.
The Visual C++/C runtime library contains numerous functions for
date and time calculations. For example, the following data types
are used in Visual C++:
Data
type
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Range
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Where
found
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COleDateTime, DATE
VARIANT
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1/1/100 through
12/31/9999
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OLE/COM
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time_t / CTime
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1/1/1970 through
1/18/2038
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C runtime / MFC
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struct FILETIME
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1/1/1601 through
12/31/58457001 (the number of 100 nanosecond intervals since
1/1/1601 in a 64-bit value)
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Windows
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struct SYSTEMTIME
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1/1/1900 through
12/31/32767
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Windows
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DOS DateTime
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1/1/1980 through
12/31/2108
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DOS
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The
operational range for Visual C++, 1/1/1980 through 1/18/2038, was
determined by combining the time_t/Ctime range of 1/1/1970 through
1/18/2038 and the DateTime range of 1/1/1980 through 12/31/2108.
Microsoft's Year 2000 compliance testing is intended to establish
the durability of our products' functionality through at least 2035.
Even when a Microsoft product is used after the upper limit of its
operational range, many/most functions continue to work fine.
Which Microsoft products include the C Runtime library
with ANSI standard time_t?
ANSI
time functions based on a 32-bit version of time_t are included in
the Microsoft Visual C++ Runtime (MSVCRT) library.
The MSVCRT library currently ships with many Microsoft
applications, including the following:
- All Microsoft development tools
- Windows 9.x, Windows 2000, and Windows NT operating systems
- Microsoft Access, Excel, PowerPoint, Project, Word, Works, and
WinCE products
A very large number of other externally developed PC applications
also use time_t.
The Microsoft C Runtime library is a redistributable file and so
any application built with Visual C++ can potentially ship with it.
However, just because MSVCRT is used doesn't mean that the time
functions based on ANSI time_t are used.
Is there any way to know for sure if my applications have the
time_t data type?
Source Scans are a way to determine this. The exact roll over
behavior will be application dependent. The ANSI standard does not
define the behavior of using dates beyond 2038.
Is there a workaround programs that were developed with 32-bit
ANSI C time functions?
Not a simple one. As with any software, if you have the source
code, you can rewrite it to handle dates beyond 2038.
What is Microsoft doing about the Year 2038/ANSI time standard
issue?
Microsoft plans to include an improved version of the time
libraries in the next release of Visual C. The new version will be
based on a 64-bit time_t data type that can handle dates through
2999.
Because time_t is an ANSI standard, no single software
manufacturer has control over its design specifications. Microsoft C
and C++ programs use ANSI standard data types to represent
dates and times internally.
Many programs use the current time_t standard and if it is
changed, applications that rely on the ANSI standard behavior could
break. For the near-term, this standard ANSI interface must be left
"as is" for compatibility reasons.
A number of 64-bit processors are now available, and hardware
vendors are rapidly making the transition from 32-bit to 64-bit
architectures. But the year 2038 issue is caused by software. Even
if the computer has a 64-bit processor, older 32-bit programs and
newer programs with time functions based a 32-bit version of ANSI
time_t will still be subject to the 2038 limit. To ensure they can
handle dates in the year 2038 and beyond some 32-bit "legacy"
applications, such as database management systems running on
mainframes or minicomputers, may have to be re-coded and
re-compiled.
Programs that use 64-bit time structures will be able to record
and manipulate dates until 12/31/2999. By 2038 most programs will be
written to run on 64-bit or even 128-bit computers.
Microsoft is already working on a new generation of time
structures that will use 64-bits and plans to include an
improved version of the time libraries in the next release of Visual
C.
For more information
See the
following white papers: "ANSI and
Visual C++ Libraries," "Visual C++ and the Year
2000," "C++
Standards û What are they? Why are they important?" and "Ctime" for more information.
ALL COMMUNICATIONS OR CONVEYANCES OF INFORMATION TO YOU
CONCERNING MICROSOFT AND THE YEAR 2000, INCLUDING BUT NOT LIMITED TO
THIS DOCUMENT OR ANY OTHER PAST, PRESENT OR FUTURE INFORMATION
REGARDING YEAR 2000 TESTING, ASSESSMENTS, READINESS, TIME TABLES,
OBJECTIVES, OR OTHER (COLLECTIVELY THE "MICROSOFT YEAR 2000
STATEMENT"), ARE PROVIDED AS A "YEAR 2000 READINESS
DISCLOSURE" (AS DEFINED BY THE YEAR 2000 INFORMATION AND
READINESS DISCLOSURE ACT) AND CAN BE FOUND AT MICROSOFT'S YEAR 2000
WEBSITE LOCATED AT http://www.microsoft.com/year2000/
(THE "Y2K WEBSITE"). EACH MICROSOFT YEAR 2000 STATEMENT IS PROVIDED
PURSUANT TO THE TERMS HEREOF, THE TERMS OF THE Y2K WEBSITE, AND THE
YEAR 2000 INFORMATION AND READINESS DISCLOSURE ACT FOR THE SOLE
PURPOSE OF ASSISTING THE PLANNING FOR THE TRANSITION TO THE YEAR
2000. EACH MICROSOFT YEAR 2000 STATEMENT CONTAINS INFORMATION
CURRENTLY AVAILABLE AND IS UPDATED REGULARLY AND SUBJECT TO CHANGE.
MICROSOFT THEREFORE RECOMMENDS THAT YOU CHECK THE Y2K WEBSITE
REGULARLY FOR ANY CHANGES TO ANY MICROSOFT YEAR 2000 STATEMENT.
EACH MICROSOFT YEAR 2000 STATEMENT IS PROVIDED "AS IS" WITHOUT
WARRANTY OF ANY KIND. CONSEQUENTLY, MICROSOFT DISCLAIMS ALL
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ORAL OR WRITTEN INFORMATION OR ADVICE GIVEN BY MICROSOFT OR ITS
AUTHORIZED REPRESENTATIVES SHALL CREATE A WARRANTY OR IN ANY WAY
DECREASE THE SCOPE OF THIS WARRANTY DISCLAIMER. IN NO EVENT SHALL
MICROSOFT OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER
REGARDING ANY MICROSOFT YEAR 2000 STATEMENT INCLUDING DIRECT,
INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS,
PUNITIVE OR SPECIAL DAMAGES, EVEN IF MICROSOFT OR ITS SUPPLIERS HAVE
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NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL
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YOU. THE INFORMATION CONTAINED IN EACH MICROSOFT YEAR 2000 STATEMENT
IS FOUND AT THE Y2K WEBSITE AND IS INTENDED TO BE READ IN
CONJUNCTION WITH OTHER INFORMATION LOCATED AT THE Y2K WEBSITE,
INCLUDING BUT NOT LIMITED TO MICROSOFT'S YEAR 2000 COMPLIANCE
STATEMENT, THE DESCRIPTION OF THE CATEGORIES OF COMPLIANCE INTO
WHICH MICROSOFT HAS CLASSIFIED ITS PRODUCTS IN ITS YEAR 2000 PRODUCT
GUIDE, AND THE MICROSOFT YEAR 2000 TEST CRITERIA.
ANY MICROSOFT YEAR 2000 STATEMENTS MADE TO YOU IN THE COURSE OF
PROVIDING YEAR 2000 RELATED UPDATES, YEAR 2000 DIAGNOSTIC TOOLS, OR
REMEDIATION SERVICES (IF ANY) ARE SUBJECT TO THE YEAR 2000
INFORMATION AND READINESS DISCLOSURE ACT (112 STAT. 2386). IN CASE
OF A DISPUTE, THIS ACT MAY REDUCE YOUR LEGAL RIGHTS REGARDING THE
USE OF ANY SUCH STATEMENTS, UNLESS OTHERWISE SPECIFIED BY YOUR
CONTRACT OR TARIFF.
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