You should probably copyright from the first registered date to the current date, especially as Dani has made changes to both the UI and the API this year.
I'm not sure how it works in the US but in the UK and EU typically you would include the start and end date of something as dynamic as a web system, to ensure that you protect your future iterations. Your registration would cover a number of years (typically 5) before you needed to re-register your copyrighted works.
Yeah, the copyright should normally state the period that it covers: from the date that the material was written to the date that the material was last modified. That has always been my understanding. I don't know if this is a requirement or not, but it is certainly the conventional thing to see.
Are you kidding? You really thought Dani copyrighted the site just last year?
Technically, the copyright refers to the site itself, i.e., the web-pages accessible to the public. It doesn't necessarily include the Daniweb brand or company, or any of it's back-end. The notice is there to tell people who can access it that they cannot copy it. Things that are not accessible are not accessible, period.
Then again, I'm not sure if Dani should put the start date of Daniweb as the start of the copyright or the start of the latest overhaul of the site. Most likely, she should start the date at the creation of Daniweb, because the overhaul was not integral (graphics, theme, the color purple, etc.., all stayed mostly the same).
And even if the copyright notice was not up-to-date, it wouldn't really change much. Technically, people might "steal" anything that was modified after the end of the copyright notice, but only the modifications, which kind of like stealing a patch from a software, but not the software itself, pretty much useless.
Like I say, in the UK you register yourself with an agency which maintains your copyright.
The registration to an agency that maintains copyrights is really nothing more than a guarantee that if someone steals your work, you'll be able to prove that you deposited the copyright first, through that agency. However, they do not "grant" the copyright, you always have copyright to your creations on the day that you create the material. However, proving that some material originally belonged to you can be a very difficult task, and registering will help with that (like having the serial number of your stolen computer helps in proving that a given computer is your stolen computer).