IMHO you’re way to go would be the Astro Binding: http://docs.openhab.org/addons/bindings/astro/readme.html
combined with rules that fire at the different events like sunrise, sunset, dusk etc.
On the plus side, the events autocalculate so no need to download/update a list.
Also, the rules run inside OH so no need for a separate webserver.
This thread might give you further ideas:
