This is one of the best Golden Hour calculators that I've found (or been led to as is the case here). Mac and PC compatible. It's free and very functional. Check it out
I used it for a shot that I took in Big Bend National Park the next day. I was attempting to get the sun shining "down" Santa Elana Canyon. The program predicted 5:00 pm. I was there at 5pm and sure enough the canyon was lit. The altitude of the sun was higher than I wanted it to be but I didn't look specifically for that (could have) so I would have to say that it's pretty well right on the money IF you know what you are doing with it. His instructions are great btw