The date on the Nuxeo document is set to the current date because that's the date the Nuxeo wrapper document is created (not the attached binary object). There is no switch/configuration capability to change that basic functionality.

If you wish to preserve the file date then you could: (a) create a custom field to save the file date, or (b) Nuxeo doesn't recommend doing so, but you could change the dublincorelistener class to modify its behaviour. Both appproaches require customization, but (a) will be easier to maintain long term. Making changes to the dublincorelistener is possible but more involved.