Great question! Before we had watches or clocks (or laptops or cell phones) to read off the time, people used other techniques to approximate the time. These techniques use the sun, the moon, and/or the position of stars to determine about how far into the day and how far into the night it is. These techniques still come in handy if you are outside without a watch.

For example, during the day, you can observe the track of the sun across the sky. When the sun is the highest in the sky and at the center of its track, it is about 12 noon. The actual time depends also on where you are in your time zone and whether or not it's daylight savings time. In the morning, the sun will be in the East and in the evening, the sun will be in the West. You can figure out about what time it is by how far above the horizon the sun is. For example, if you know the sun rises at about 6 am and sets at about 6 pm (typical in early spring and late summer), and the sun is in the East halfway between the horizon and overhead, then it is about 9 am.

Of course, these techniques can't tell you down to the minute or second what time it is, and for that, you do need to refer to a time-keeping device like a watch.

You sure can tell time without a clock or a watch! Time passes regardless of whether you're keeping track of it or not. While you won't be able to tell time in seconds or minutes without a watch, you can still guess the hour or general time of day. One of the oldest ways of telling time is the sundial, and it still works. Sundials work by casting a shadow on a disk marked with different periods of time. As the sun moves in the sky, the shadow falls on a different part of the disk, which gives the time of day. Sundials don't work well at night, though, as you can imagine.