Sundials use the shadow cast by the Sun to tell the time since ancient times and they did a great job. The shadow of the Sun was also used by the ancient Greek thousands of years ago to determine Earth's circumference. All over Earth, people built sanctuaries and places where the shadow of the Sun at different times of the day tell us no only the time but also the history of time on Earth. Starting with a stick in the ground and finishing with very complicated structures, where the Sun at noon spreads its light on a golden plate that marks the beginning of the year, we all used the Sun, all over the globe to tell the time. It's our best tool.
Even the Mars exploration Rovers are carrying the first sundial made for Mars ahead of man's arrival. Since I am trying to teach my team how to navigate without instruments constructing a Sundial is the logical first step to start. One Martian day is called Sol, since the Viking lander days in 1970's and it's 24 (Earth) hours, 39 minutes and 35,2 seconds long. It's longer than the normal day on Earth. Our Sundial will not tell us the time on a 24 hour basis, more like from 8-5 and this is why we decided to nick name it the "8-5 + 1 hr lunch break" dial, to remind us of the fact that home, on Earth, most of the people have a 9-5 job. It's real name is "Sarmisegetuza", our ancient capital of Dacia where our ancestors had an astronomical sanctuary, measuring the time and predicting the eclipses using the Saros cycle.
The reason we can only have it from 8-5 is position. At 5 PM the shadow cast by the hills nearby is ending all our fun.
We can see our dial from the kitchen's window and if the generators would stop working we could send someone from time to time to stand there for as long as the food will have to broth so it's coming in quite handy.
Building our Sundial in few easy steps
We started by deciding where about will it go. "Erlay in the Morning" we went up to decide where it should be: 
