AI, which isn't guaranteed 100% accurate, offers this...
"WavePad does not appear to offer a built-in option to preserve the original file’s filesystem timestamps when you resave an edited audio file; its help documentation covers saving, file types, and working with files, but not timestamp preservation.help.
What this means
When you save a processed file, Windows will normally treat it as a newly written file, so the modified date changes. That is standard behavior for most editors unless they explicitly add a timestamp-preservation feature, and I could not find one documented for WavePad.
Practical workaround
If keeping the original date/time matters, the usual approach is to save the edited file with a new name and then use a file utility or PowerShell to copy the original file’s timestamps onto the new file afterward. WavePad’s documentation also shows that it supports normal “Save File As” workflows, which makes that workaround practical.
Example
On Windows, a quick post-save fix is to copy the original file’s timestamps to the edited file using a tool or script rather than expecting WavePad to do it internally. That preserves the original created/modified dates even though the audio content has changed,"