it is a simple explanation of where the sun is, and you can roughly gauge it in the same period, or do it with a sun calculator - not sure if i've gotten the name right.
there are even landscape photographers who plan ahead for an entire year, to hide inside a cavern leading to the sea.. they wait for the time when they think the sun will hit the end of the cavern to get the composition they want.
luck? luck is when you take a picture of a street corner and capture a falling body of someone who decided to commit suicide.
luck is when you were there when 9/11 happened, out of harm's way, and managed to capture the situation.
landscape photography is less of luck, but more of thinking, perserverence and never-say-die attitudes.