Watch Complications Explained
Calendar & Moon Phase
Day display, Date display, Month display Are the simplest and most obvious of complications revealing the Day, Date and Month, and generally displayed on a rotating wheel visible through an aperture.
Leap Year complications display successive years as 1, 2, 3 and 4, with 4 indicating the leap year.
Perpetual Calendar is one of the most complex types of calendar features on a watch displaying the date, day, month, and year, and even takes into account the leap year. These complications are expensive to producing making them relatively rare.
A day/night indicator shows which half of the day corresponds to, typically, a 12-hour time display.
Moon phase follows the progression of the moon through its different phases of the new moon, first quarter, full moon and last quarter. The display utilizes a rotating disk viewed through an aperture on the dial to indicate the cycle of the moon, showing the illuminated portion of our moon, as it would be seen from Earth.
The Equation of Time incorporates all the features of a standard perpetual calendar with an additional feature to measure in minutes, of the difference between our “calendar time” and the actual “solar time.”
Sunrise time, Sunset time, Length of day, Length of night give the further details of the day displaying through an aperture on the dial.
Seasons, solstices, equinoxes and zodiacal signs – indicates Solstices (when the sun is at its furthest or closest point from the equator) and Equinoxes (when night and day are equal lengths) as well as tracking Zodialogical signs through icons.
Tide level indicator as it suggests, this gives the state of the tides ebb and flow.
Sun-Earth-Moon conjunction indicates the position of the celestial bodies in relation to each other.
Celestial Chart is a sky chart giving the position of the moon in relation to the stars from a particular hemisphere.
Celestial time, minutes, hours or “sidereal hours”
Sidereal time is a time-keeping system that astronomers use to locate celestial objects. Using sidereal time based on the Earths` rate of rotation relative the fixed stars, it’s possible to point a telescope to the correct coordinates in the night sky.
All The Other Stuff
Tourbillon is a small rotating cage that houses the balance, hairspring, and escapement. The rotation of the tourbillon effectively eliminates the pull of gravity on the accuracy of the watch.
Power Reserve Indicator simply measures the amount of power remaining in the watch by the tension of the mainspring and displays it. This is exclusively found in mechanical watches.