modification dates on downloaded files

[ClarkePeters]

Ubuntu natty

I often arrange my files by modification date so that I can see what the last things were that I was working on. Sometimes when I download a file or video the modification date is the download date and sometimes it is the date of creation or modification of the original owner (e.g. I download the file today on 1/1/2011, but the modification date is 2/4/2008, or something like that.)

How can I prevent this behavior or get all my modification dates to automatically be the download date.

[ClarkePeters]

anyone?