Our first glimpse of time-keeping tools (i.e., not estimating based on the position of the sun) comes from The Babylonian Empire. Using a large amount of observations on the path the Sun traversed through the sky, they succeeded in creating the first clock. A stone pillar was stuck in the ground with furrows cut into the surrounding land. By measuring on which furrow the ]shadow] of the pillar landed, the Babylonians had made the first non-human time-keeping device.
In the Asterix series of comics, a tall pointed menhir is often seen during their travels to Egypt. This was not a menhir at all -- it was a sundial. These huge structures were named 'Cleopatra's Needles' by the Romans. The Egyptian day was divided into 12 parts, each being (obviously) about two modern hours.
The Egyptians also succeeded in building a portable time keeping device as they realised that it would be somewhat inconvenient to lug around a stone pillar to tell the time. They built a small sundial on a peice of metal or wood known as a 'style'. This had the advantage of portability. There was an inherent problem with sundials, however -- they only worked in the sun. This meant that on cloudy days, or at night, a sundial was completely useless.
500 years, later, the Egyptians, always innovators, found a solution to this problem -- the water clock. Two jugs were kept, one directly on top of the other. The top one wa siflled with water and had a hole drilled in the bottom. As the water level decreased, people could check the time by seeing how far the level had dropped. But this also had a problem -- during cold weather (which I suppose was not too common in Egypt) the water clock would freeze.
Around 250 B.C the hourglass was invented. It was a modified version of the water clock (it used sand), but if the humidity was high, the sand got stuck. Another problem. Also around this time, the candle was used as a timekeeper. The rate at which the candle melted was measured and used to tell the time.
The mechanical clock was invented during the Middle Ages. These clocks used chains, weights, gears and springs to turn a pointer on a clock face. Most were huge affairs, put up on cathedral towers so that the whole town could see the time. These mechanical clocks finally became portable in the 16th century when German watchmaker Peter Henlein created the mainspring. This tightly coiled spring unwound slowly, powering the clock as it did so. Many modern clocks use a mainspring -- these are the clocks that must be wound up once or twice a day.
Around this time, the term 'watch' was introduced. The origin of the word is due to the fact that the town guards, or watches carried portable watches on straps, These clocks became known as watches also.
In 1656, Christian Huygnes, a Dutchman, used Galileo's work on the regular motion of pendulums to design the first pendulum clock the world had ever seen.
An interesting watch was that belonging to Mary, Queen of Scots. She wore her watch as a necklace with a small skull at the end. To see the time, she would turn over the skull and the jaw would open revealing a dial. Since then, clocks have progressed hugely. Today, we have TV watches, calculator watches, xclock and countless others.