Ah, ok, now I understand.
I don't know how Windows works, when it extracts files from a zip. What happens if you extract the zip file, using DotNetZip? Do the file timestamps get set the way you expect? What happens if you extract another zip file, one not
created by DotNetZip? (Maybe it's created by Windows as a compressed folder.) Do you get files with the expected values for the 3 timestamps?
When creating zip file with DotNetZip , by default each entry will get its created, lastmodified and last accessed timestamps set, internally in the zip entry metadata. You may have seen the documentation that describes this timestamp
information as being stored in an "extra" field inside the zip file. The "extra" field is part of the zip specification, but it was added after the original zip format was created. As a result, not every zip tool or library
reads or writes the extended timestamps. DotNetZip does.
Once you have a zip file with the extended timestamps, it is then up to the extracting application or tool - in your case Windows Explorer I guess - to apply those timestamps to the files it extracts. I don't know if Windows does this. It wouldn't
surprise me to learn that Windows doesn't take advantage of the extended timestamps, but I don't know.
That's why I asked what happens if you extract with a DotNetZip application. In that case, if the timestamps on the extracted files match what you expect, it indicates the timestamps are correctly set in the zipfile, and they are being used
upon extraction. I'd be very surprised to hear this is not the case. I have a number of tests covering this in the test suite that I run before posting a release. I don't have a test case to check the resulting file timestamps for the situation
where Windows is used to extract. You should be able test that pretty easily.
Windows supports zip files, but not all aspects of the ZIP specification. One thing it doesn't support is UTF-8 encoding for entry names. It also does not support WinZip encryption. It's possible that Windows also doesn't support the extended