Robert A. Macy wrote:
Today, on the Win98 machine, several files suddenly had their modified
and created dates changes to December 5, 2009 !!

If this is really, really important-- maybe wait a bit for additional
input. Try this Google search too...
http://www.google.com/search?hl=en&q...&aq=f&oq=&aqi=

http://support.microsoft.com/kb/132627
ScanDisk Reports Invalid Date/Time for Many Files

A Modified Date is the date a file was last written to. A Created Date
is the date a file shows up in a folder. Those can be the same date, if
a file is created for the first time in a folder & is never modified
after that. If later modified, Modified Date will be higher than Created
Date. But most original system files were last modified on 04-23-1999 &
moved to your folder later. Those have a higher Created Date.

To get Created Date to be the current date, move it out & then back in
to its current folder. I'm not sure whether Windows will just give an
error message, though, if it sees the Created Dated to be later than the
current date. If so, run ScanDisk first. That will set Created Date to
01-01-1980.

To get Modified Date to be the current date, run ScanDisk. Be sure to
set your system date to the current date first. Also, click the Advanced
button & ensure ScanDisk is set to fix the dates.

Some files created in 2007 had their modified date changed to December
3, 2009

So, some Created Dates remained the same while the Modified Date changed
& others did not? Files already present retain the original Created Date
while getting a new Modified date. Other files created for the first
time will have the same date for both, until they are modified again.
Then, the Modified Date is higher.

Today after much problems I discovered my calendar set to December 5,
2009, although I did not change it.

I presume you mean the system date. Have you clicked the clock in the
Tray yet & changed it back?

How do I change them back to the appropriate dates?

The changes span over several folders, too. I don't even know how to
look for all the damage to undo it.

ScanDisk will go through all the folders. Here is a sample of what it
can do from my ScanDisk.log...

The C:\Program Files\NetZero\images folder contained incorrect
information about nz_plt_search_text.gif (MS-DOS name NZ_PLT~1.GIF):
The last-modified date or time for the file or folder was invalid.
Resolution: Repair the error
Results: Error was corrected as specified above.

I remember getting asked whether to make the change. Too bad it doesn't
show the actual dates it changed.

I would normally ignore and just let the calendar 'catch up', but
these folders are synchronized in four locations using xcopy and the
most recent date stamp. I don't dare allow these files marked with
weird dates to corrupt the updating processes.
help!

Robert

--
Thanks or Good Luck,
There may be humor in this post, and,
Naturally, you will not sue,
Should things get worse after this,
PCR