The name Zephyros comes from Greek Mythology. Zephyros was a son of EOS and the brother of Boreas and Notos.

The Zephyros is presented in Martin Braun’s signature case, but with a clear and elegant new design. Inspired by a sextant and the sextant scale, the Zephyros symbol is engraved in the handmade, three-dimensional guilloché dial. Featured on the bottom of the dial are the season indicator and the equation of time register. The season indicator displays the current time of year – spring, summer, fall or winter. The equation of time register displays the difference between real and mean time.

The irregular daily movement of the sun was known by the Babylonians, and Ptolemy has a whole chapter in the Almagest devoted to its calculation. However, he did not consider the effect relevant for most calculations as the correction was negligible for the slow-moving objects in the sky. He applied it only for the fastest moving luminary, the moon.

Until the invention of the pendulum and the development of reliable clocks toward the end of the 17th century, the equation of time, as defined by Ptolemy, remained a curiosity, not important to anyone except astronomers. Only when mechanical clocks started to take over timekeeping from sundials did the difference between clock time and solar time become an issue. Apparent time (or true or real solar time) is the time indicated by the sun on a sundial, while mean solar time is the average as indicated by clocks.

The equation of time is the difference, over the course of a year, between time as read from a sundial and a clock (apparent time versus mean time). The sundial can be ahead (fast) by as much as 16 minutes 33 seconds on November 3 (the longest day of the year), or fall behind by as much as 14 minutes 6 seconds on February 12 (the shortest day of the year). It is caused by irregularity of the motion of the sun in the sky, due to a combination of the obliquity of the earth's rotation axis and the eccentricity of its orbit. The equation of time is the east or west component of the analemma, a curve representing the angular offset of the sun from its mean position on the celestial sphere as viewed from earth.

Until 1833, the equation of time was mean minus apparent solar time in the British Nautical Almanac and Astronomical Ephemeris. Earlier, all times in the almanac were in apparent solar time because time aboard ships was determined by observing the sun. In the unusual case that the mean solar time of an observation was needed, the extra step of adding the equation of time to apparent solar time was needed, requiring all differences in the equation of time to have the opposite sign. Since 1834, all times have been in mean solar time because the time aboard most ships was determined by marine chronometers.