Actually you need two clocks. One set to GMT and one set to local if you want to establish your longitude. But GMT wasn't even established in Great Britain until 1880. And using time to establish longitude wasn't developed until Harrison built his marine clocks around 1741. And, even then, it took until 1800 for those to be in general use.

And compasses weren't invented until 250 BC by the Chinese and about 150 years later by the Europeans. People had been sailing for several centuries before that. The Polynesians and other Pacific peoples had been sailing for centuries before that without aid of compass, charts, sextant or written language. And, unlike Columbus, they were aiming for tiny little fly specks in the middle of a vast ocean, not a huge land mass.

And, lets not forget, that hominids have been wandering all over this planet for thousands of years before that. No compass, no writing, no charts and, probably, only a rudimentary language.

And let's go back even further and even further down the evolutionary ladder. Whales (okay not down the ladder) and other cetaceans navigate vast distances without technology. Birds navigate vast distances without technology. Going back further, there is even evidence that dinosaurs migrated vast distances. And let's not forget monarch butterflies. They navigate thousands of miles and even generations with only a rudimentary brain.

I've tromped the wilds of Colorado for decades and I've never carried a compass. I seldom carry anything other than the map in my head. I don't need a sextant or almanacs or mathematical tables. Nor do I need a GPS (much less 2) to navigate. I rely on my knowledge of drainage basins, peaks, landmarks and where the sun is to get around. I've only ever been 'lost' once and, even then, by keeping a calm head and a keen eye, I was able to back track to my original route and get out of the forest.