Run a script based on sunset and sunrise info?
Never used this, but it looks like Power Manager should be able to do it. You can make sun based actions similar to automator. 

It doesn't seem like it has a feature built in to figure out your location automatically though. So if you're like flying from country to another and want it to automatically figure it out, you probably can't do that.

They have a tutorial: How to Power On Your Mac at Sunrise
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