Written by Grégory Gardinetti, CNN

Grégory Gardinetti is an expert and historian in watchmaking and the Culture and Patrimony Manager at the Fondation de la Haute Horlogerie in Geneva. The views expressed are his own.

I love watchmaking in all its forms but astronomical complications are for me, the most magical. With astronomy you have the universe, the infinite, the giant -- whereas with watchmaking, you have the tiny, the minute.

But astronomical complications (additional watch features that display the movement of heavenly bodies) are the best of both worlds. They offer you the unique opportunity to have the universe on your wrist. It's impossible for me not to start dreaming when I see a moon phase on a dial.

The origins of time-keeping

The annual Geminid meteor shower appears over Elva Hill, in Maira Valley, in northern Italy on December 12, 2015 Credit: MARCO BERTORELLO/AFP/AFP/Getty Images

The primitive man understood the notion of time at a very early stage. This concept wasn't broken in hours as we know them today, but based on the passing of day and night, as well as seasonal cycles, with the sun and moon as reference points.

Repetitive patterns on engraved bones, pottery fragments, and rock paintings suggested the nascent stages of a calendar.

The first known astronomical observatories

First visitors inspect the reconstructed sun-observatory in Goseck, eastern Germany, during the site's inauguration on winter solstice December 21, 2005. Credit: JENS SCHLUETER/DDP/AFP/Getty Images

Megalithic art, or art carved into large stones, emerged around 5,000 B.C. across the globe. These revealed the first techniques used in an attempt to trace the course of the moon and the sun.

The Goseck circle in Germany, or Stonehenge in England are, among other examples, the first known astronomical observatories.

Some of them indicate the date of the winter solstice -- the shortest day of the year, and when days after, start to grow longer -- matching the resumption of agricultural work that was essential to the survival of the population.

Others mark the date of the summer solstice, which ushers in the harvest period. For some archaeologists, some of these megaliths were arranged in such a way that it would mirror the course of the moon during its cycle, a duration of 19 years as it would be later become known, as well as the course of the sun throughout the year.

The crisscrossing of these trajectories made it possible to anticipate a solar eclipse.

Calendars came next

Reindeer are seen silhouetted against the moon during a lunar eclipse in Minsk, Belarus on September 28, 2015. Credit: SERGEI GAPON/AFP/AFP/Getty Images

To be able to set time and historical references, such as foretelling harvests and hunting periods, man developed calendars, relying mainly on phenomenon easy to observe from the Earth: lunar or solar cycles. Thus, ancient Roman calendars were lunar.

The phases of the moon provided simple and an easy means by which to measure time. Their cycles, with an approximate length of 29-and-a-half days, helped define the 12 months of the year.

This affiliation is recognizable in the English and German languages where the noun "moon" gave its name to "month."

The week then, did not always consist of 7 days. Only in 312 A.D. did Emperor Constantine, newly converted to Catholicism, impose a seven-day week, to match Christian religious texts.

Prior to this decision, a week would consist of 9 or even 10 days. The adoption of a seven-day week matches the length of each of the four phases of the lunar cycle: new moon, crescent moon, full moon and sickle moon.

Time is measured

A child walks on a sundial on a square in Trest, Czech Republic. Credit: AFP/AFP/AFP/Getty Images

The complete passage of the Earth around the sun produces the cycle of the seasons -- observation of which seems to have taken more importance after the development of agriculture in the Neolithic era.

Thanks to the sun, man was able to produce the first measurements of time, which was recorded by the "gnomon," the ancestor of the sundial.

For awhile, the sundial indicated unequal hours until it was equipped with a style parallel to the axis of the Earth.

The shadows cast by its calibrated positioning allowed the display of 12 hours of equivalent length.

Earth at the center of the universe

The astrolabe, whose invention is often attributed to the Greek astronomer Hipparchus, places the Earth at the center of the universe, with all celestial bodies orbiting around it.

This system, called the geocentric model (or geocentrism), is a description of the cosmos where the Earth is motionless, at its center.

Defended in particular by the Greek scientists Aristotle and Ptolemy, this perspective lasted until the end of the 16th century, being gradually replaced by heliocentrism. This latter theory is the astronomical model in which the sun lies at the center of the universe.

Despite the forward thinking of some precursors in Antiquity, such as the Greek astronomer and mathematician Aristarchus of Samos, heliocentrism remains usually attributed to Copernicus who was born in 1473 in Royal Prussia. Scientists Johannes Kepler and Galileo Galilei later expanded his work.

During the Renaissance, the astrolabe improved the more technical and astronomical aspects of pendulum clocks and of the ecclesiastical calendar. These were the clocks that often decorated the homes of the rich and the scholarly.

From sky to wrist

Pocket watches with astronomical functions appeared during the Renaissance.

They usually gave their bearer indications such as: the date, the day, the month, the phases and age of the moon, and in some cases, even the signs of the zodiac.

As of the 18th century, new astronomical data became available on the pocket watch: equation of time, hours of sunrise and sunset for a given location, hours of the tides, maps of the sky and the stars.

Today, these various astronomical functions can mainly be found in very complicated watches, whether they are pocket watches or wristwatches.

These exceptional timekeepers are masterpieces of knowledge, technique and know-how, presenting a range of complex functions: display of sidereal time, equation of time, hours of sunrise and sunset, star charts, angular movement of the moon, phases of the moon with needles, hatch or three-dimensional, systems to predict lunar and solar eclipses, positions of the stars seen from the Earth, display of the ephemeris (solstices, equinoxes, seasons), and the signs of the zodiac.

A digital future?

It's difficult to speak about the future. Of course, you can display all the astronomical complications on a smart watch. But where is the magic? Without wheels and ticking sounds, the dream stops.

Mechanical watchmaking will keep us dreaming into the future.

See gallery above for starry timepieces.