I read in another post about importance of an updated file date. I understand it pertains to when pages were last updated. How may I ensure that my pages "file dates" change when updated?

I don't think there is much importance to place on whether your file date is updated. You really just look at the cache and see if Google has your current content. I don't even see a date when I pure search for my URL, just the updated content in the cache. But in answer to your question, I think it is purely up to Google.

If you have PHP access then you can echo the date into the HTML page, either in the visible body content, or into a comment field in the code. When you check the Google cache then you will always be able to see the exact date and time that Google took that page from your site.

Also see RFC 3339 for date formats used with time stamps (i.e. YYYY-MM-DD and HH:MM:SS with UTC time zone).

Google does seem to give some sort of favor to pages that have been updated recently. This all lies in the if-modified-since information which is available to all search engine spiders when they crawl your page.

It doesn't matter if the date and time is populated automatically on your page, that's not enough to modify the if-modified-since information.

You actually need to make changes to you page(s) to update the file date.

By the way--the Google cache has nothing to do with this.

Thanks all, bhartzer - I read here somewhere that Google can't read the "updated since" if the site isn't set up correctly on the server )not in how the pages are constructed). I have no idea as to what that would be or if it's even correct. I've tried like #$%^ to find the reference but... No Luck

For what it is worth file date defiantly has something to do with ranking. It has been on my list of maintenance items for sites I optimize for some time now. I do notice that all things constant my sites have a tendency to drop slowly. But when I change the file last updated date by changing something on the page things usually pick up where they were.

FIRST: bhartzer is absolutely right on this one.

SECOND:

Thanks all, bhartzer - I read here somewhere that Google can't read the "updated since" if the site isn't set up correctly on the server )not in how the pages are constructed). I have no idea as to what that would be or if it's even correct. I've tried like #$%^ to find the reference but... No Luck

I have sites where the header information delivered to spiders does not contain the "if-modified-since" date, but it does not seem to matter to the spiders. Some how, they seem to recognize that a file is fresh (recently replaced).