Dates can be a clue, but you shouldn't go by that alone. The operating system and your programs will create or modify different files as part of their normal operation, so the fact that a file was modified/created on a date that you didn't manipulate any files isn't an absolute indication that the file is malware-related.

Some other fators that can help you determine whether a file is malicious or not:

* The exact time of creation/modification. If you find a clump of files whose timestamps (as well as datestamps) are identical or very close, chances are good that the files were created/modified by the same process.

* No identifying information (version #, company name, etc.) in a file's properties pages. Such "anonymous" files are always worth looking into.

* Random or "garbage" filenames. For instance, common sense should indicate that a file named "11Fßä#·ºÄÖ`I" just might be malicious.

* Files whose names are almost identical to normal/legit files: scvhost.exe instead of svchost.exe, for example.