Simon: 10/10/2013 - 03:00 PM
Search engines don't pick up the date mentioned on page. They show the actual date, when the article was first published - just like we do.
Changing a few parts of the content doesn't make it a whole new article. Which is why Google doesn't change the date. If you rewrite the whole content, however, then there is a chance Google might notice this and change the date, too. However, why would anybody do that? In such a case it's probably a better idea creating a new article from scratch and leave the old one untouched.
I'm sorry but that's completely incorrect - and I can prove it!
Consider the following page I have on Zujava (which publishes without dates):
http://www.zujava.com/tassimo-single-serve-coffee-makers
If you put the url in the search engines it will say this in the blurb under the url:
"Aug 5 2013 - There are many different brands of single cup coffee makers, and this page will be reviewing the Tassimo and comparing it to it's main rivals."
If you look at the page you can see that at the bottom it has a note from me that says "Updated: August 5 2013"
The page was in fact created in November 2012 and the wayback machine has a capture on May 18th 2013:
http://web.archive.org/web/20130518065350/http://www.zujava.com/tassimo-single-serve-coffee-makers
Feel free to check this out for yourself by putting the url into the serps and checking what date is displayed and checking out the waybackmachine's date. But it conclusively proves that the date displayed in the serps is the one on the page rather than the date first indexed.
If you are uncomfortable with having the last date updated being displayed, then remove the date altogether. But don't invent stuff about what the search engines do - observe what actually happens!
The date displayed affects the click through rate. Have you seen any content in the SERPs dated say seven or eight years ago? No, and that's because Google's user monitoring has indicated that people refuse to click through on anything with an "old" date. For example: Squidoo was created about seven years ago but they don't display dates either - for the very good reason that no-one would click on an article that was originally created in 2007 or whenever with the date on display.
News needs to be dated but evergreen content does not. I'm guessing from your comment that you believe Wizzley to be a news site rather than a repository of evergreen content?