The Equation of Time is a horological complication that represents the discrepancy between solar time and mean time. Solar time, which is based on the apparent motion of the sun across the sky, varies throughout the year due to the Earth's elliptical orbit and axial tilt. Mean time, on the other hand, is a standardized measure that divides the day into 24 equal hours. The Equation of Time quantifies the difference between these two times, which can be as much as 16 minutes fast or slow depending on the time of year.

In watchmaking, the Equation of Time is a sophisticated feature found in high-end mechanical watches. It is typically displayed on the watch dial, often through a sub-dial or an additional hand, providing a visual representation of the time difference. This complication is valued for its technical complexity and the skill required to integrate it into a timepiece. It serves as a testament to the watchmaker's craftsmanship and understanding of astronomical phenomena. Collectors and enthusiasts appreciate watches with this feature for their ability to connect the wearer with the natural rhythms of the Earth, offering a deeper appreciation of time beyond the conventional hours and minutes.