Timepiece comprising a day/night display that takes account of seasonal variations

A timepiece comprising:

• a timepiece movement;
• a calendar mechanism;
• and
• means for indicating the sunrise and sunset that take account of seasonal variations,
• the timepiece movement comprising a minute wheel set, a motion-work, an hour indicator member, and an hour wheel set integral in rotation with the hour indicator member and arranged to be driven by the minute wheel set via the motion-work either at a speed of one revolution in 12 hours, or at a speed of one revolution in 24 hours,
• the calendar mechanism being arranged to be driven via the hour wheel set and comprising a date display and a month display,
• the sunrise and sunset indicating means comprising a sphere that replicates the terrestrial globe and a ring mounted concentrically to the sphere and arranged to indicate the position of the earth's terminator, the sphere being arranged to be driven in order to rotate, at a rate of one revolution in 24 hours, about a first axis corresponding to the polar axis of the terrestrial globe, and the ring being mounted in order also to be able to pivot relative to the sphere about a second axis intersecting the first axis perpendicularly at the centre of the sphere, the sunset and sunrise indicating means further comprising an annual cam having a profile representative of the tilt of the sun with respect to the equatorial plane, and arranged to be driven in rotation at a rate of one revolution per year, the plane subtended by the ring forming with the first axis an angle equal to the angle of tilt of the sun with respect to the equatorial plane;
• wherein all months of the calendar mechanism include 31 days such that the calendar mechanism is a simple calendar mechanism,
• wherein the timepiece movement comprises a third kinematic chain connecting the annual cam to the hour wheel set via the display mechanism for displaying the month,
• wherein, either the third kinematic chain has a transmission ratio of 1:744 in the case where the hour wheel set is arranged to be driven by the motion work at a speed of one revolution in 12 hours, or the third kinematic chain has a transmission ratio of 1:372 in the case where the hour wheel set is arranged to be driven by the motion work at a speed of one revolution in 24 hours, and
• wherein the third kinematic chain comprises a reduction gear train with a ratio of 1:744 and comprising a reduction wheel set which comprises an 18-tooth pinion and which is integral in rotation with the hour wheel set, the pinion of the reduction wheel set meshing with a 36-tooth wheel of a first intermediate wheel set arranged to complete one revolution in 24 hours, the first intermediate wheel set being provided with two fingers arranged respectively to advance step-by-step, once in 24 hours, a date star-wheel comprising 31 teeth, and a 40-tooth star-wheel of a second intermediate wheel set, the second intermediate wheel set further comprising a 10-tooth pinion coaxially integral with the 40-tooth star-wheel, the 10-tooth pinion being arranged to mesh with a toothing of 93 teeth of an annual wheel set on which the annual cam is mounted.