DOCUMENT:Q58495 17-DEC-2000 [msdos] TITLE :MS-DOS System Date Cannot Have a Year Past 2099 PRODUCT :Microsoft Disk Operating System PROD/VER:MS-DOS:3.x,4.x,5.x,6.0,6.2,6.21,6.22 OPER/SYS: KEYWORDS: ====================================================================== ------------------------------------------------------------------------------- The information in this article applies to: - Microsoft MS-DOS operating system versions 3.1, 3.2, 3.21, 3.3, 3.3a, 4.0, 4.01, 5.0, 5.0a, 6.0, 6.2, 6.21, 6.22 ------------------------------------------------------------------------------- SUMMARY ======= The year portion of the system date has 7 bits for storage (0-127). MS-DOS offsets the year from 1980; therefore, the maximum value for the year should be 2107. However, due to a ROM BIOS limitation, 2099 is the maximum value. The description for interrupt 1AH details the implementation causing the limitation. MORE INFORMATION ================ The ROM-BIOS interrupt 1AH deals with BCD (binary coded decimal) numbers. Each decimal place is represented by 4 bits. The century is returned in CH (either 19 or 20). CL contains the year. Each byte can have a value ranging from 0 to 9. The numbers returned are absolute values, not offsets from 1980. Thus, the maximum value for the (decade) year is 99. With the century returning 19 or 20, the maximum year (century-year) is 2099. Additional query words: 6.22 3.20 3.21 3.30 3.30a 4.00 4.01 5.00 5.00a 6.00 6.20 ====================================================================== Keywords : Technology : kbMSDOSSearch kbMSDOS321 kbMSDOS400 kbMSDOS320 kbMSDOS330a kbMSDOS621 kbMSDOS622 kbMSDOS620 kbMSDOS600 kbMSDOS310 kbMSDOS500 kbMSDOS330 kbMSDOS401 kbMSDOS500a Version : MS-DOS:3.x,4.x,5.x,6.0,6.2,6.21,6.22 ============================================================================= 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 2000.