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Those are macOS system files and the creation/modified date reflects when Apple created them. If you were to copy them, then the date can change even if the file hasn't - it depends on the options used when copying. If the copy to your computer was done such that the original date wasn't preserved then the date would need to be when your computer was active.

 

Typically, when files of the type you had in your original post are installed on a Mac, Apple will retain the created/modified date when it is copied over. So the date will not reflect when it was copied to the computer. However, if for some reason, those files were copied without the option to preserve the original created/modified date, the date will change to when it was copied. This would be unusual. You erased your original post but if I recall correctly it was the /usr/bin directory you were showing was the date sometime in April? On my High Sierra computer, looking at the dates for /usr/bin for 10.13.4, the dates are March 27, which would be a couple of days before the 10.13.4 release date of March 29, 2018. In looking at these dates after doing the 10.13.5 update, it's May 29, and the release date of 10.13.5 was June 1, 2018. So you can see the pattern. I see a High Sierra Security update 2018-001 with the release date of April 24, 2018 - so maybe your files reflect that date. Again I'm not exactly sure which directory and what date it showed because you've erased your original post - there was no reason to do that - you weren't exposing anything that would compromise your security.