I've been running a photo blog for almost 8 years. The format has always been similar (same image widths etc) but now I'm looking to change it. I want to use the Autofocus+ Pro theme which is great for photographers. It has everything I want however to import 8 years worth of entries and make sure that the thumbnails etc look good is going to be impossible. My current theme is Thesis, which works fine for the existing posts.
How can I go about defining that all posts prior to 2011 use the Thesis theme, whilst all posts after a certain date use the Autofocus theme?
My blog is www.funnytimeofyear.com.