"Date Modified" doesn't change after Overwrite

Just recently, I've noticed an issue where the directory field "Date Modified" does not change after a copy/paste/overwrite using Windows Explorer.

Background Info:
To update images on several websites, I've been simply overwriting the old image files and syncing via DreamWeaver. I believe this method to update and preserve corresponding html links is a fairly standard practice in the industry. So I won't go into much detail here. The issue I'm running into is that my files are, suddenly, no longer syncing correctly after using this method for over 2 yrs. I believe it may be due to the "Date Modified" not updating correctly, but I never really paid attention to it before this issue occurred the other day.

Here's the scenario:

1) New Image files are created using Adobe InDesign and saved to a networked drive. Note: Because these tend to be recurring themes/designs, I create multiple files at once, so they have nearly the exact same Created & Modified dates to start with.

2) I open the image (PNG) with Windows Photo Viewer > File > Make a Copy > browse to my website folder and save over the old image. Note: warning dialogue clearly pops up asking me for the OK to overwrite the old file.

3) At this point, I have successfully overwritten the old image. I can open it to view the new content and (until recently) sync it to my remote folder with no issues. However, the other day I noticed that even though I could open to see the new content, the thumbnail was displaying the old content and the modified date was not the current time/day even though i had just overwritten it. (Same issue happens when I Copy/Paste/Overwrite).

4) After testing the copy/paste function, save as, and make a copy functions, I noticed that this issue is the same across the board for all files types. The modified date doesn't seem to update to the current time/day on the overwritten file. It seems to maintain the original modified date from the copied file.

5) Since the modified date is seemingly unchanged (or older than the original), DreamWeaver doesn't recognize that the local and remote files are out of sync (or newer) and ignores it.

I understand the Created Date carrying over or remaining the same, but why doesn't the modified date change when it's overwritten? Am I missing something? Is this normal?

I hope I explained this well enough. I could really use the help right now.

Thanks,

G

Any ideas? I'm pissing in the wind over here

I may have exaggerated it a bit. After some further testing, this is what I've noticed.

1) copy/paste/replace seems to carry over the modified date from the copy not matter what the file is. The other file is clearly being replaced. Why doesn't that count as being modified?

E.g. File A exists in both folder 1 and 2. If I copy it from folder 1 (modified 1pm) and paste into folder 2 (modified 2pm) to overwrite that version at 3pm; it will show the correct content in folder 2, but with a modified timestamp of 1pm instead of the time is was overwritten at 3pm.

2) Opening a PNG with Windows Photo Viewer > File > Make a Copy has the same affect, even if I change the title of the copy in the process. I assume this is because it's using a "copy" function instead of a "save as".

E.g. File A (modified 1pm) in folder 1 is opened in WPV. File > Make a Copy > browse to folder 2 > browse to File B (modified 2pm) > double-click to rename the copy and overwrite File B at 3pm. File B (in folder 2) now shows the correct content (from File A) but has a modified timestamp of 1pm instead of the time it was overwritten at 3pm...

3) "Save as" function seems to be properly updating timestamps for all programs.

This all just started happening a week or so ago. I haven't tried the access timestamp yet, but I don't believe that will solve my issue since I'm concerned about the modified date (which is what DreamWeaver and other programs use to check for updates). Any other ideas?