@tonyfalcone - I had an app that did 90% of what you wanted anyway, so try this one out (I have not tested it):
For this to work, you need to have ST put you in “Away” mode when you’re not home. The way it works is this:
When ST changes modes, the app checks if the mode is to “Away” or some other mode. If Away, it will turn on the light if it’s night already or schedule the light to come on at sunset if it’s not already night. The lights will just keep coming on at sunset and off at sunrise until someone comes home (i.e., ST changes out of “Away” mode).