Can't change timezone

Patch for 3.x-dev

I'm a newer maintainer of this module. It looks like this issue is worth re-opening. I'm going to trigger the automated tests and see if anything fails. While writing the tests it looked like something was fishy because the assertions I had to write for the addtocalendar field were different from the assertions I had to write when using third party settings even though the cases appeared to me like they should give the same end result. So I'm actually hoping something fails here!

Thanks for taking over maintenance of the module @danflanagan8. I'm experiencing the timezone GMT issue with the dev version. Tried the patch and a few other things. Will report back if I find anything of importance.