Simulator of the calendarium of the Prague Astronomical Clock

Thanks to the courtesy of the author, Mr. Vlasta Filler, you can see a functional model of the perimeter of the calendar plate. We simplified the program and added textual display of current data. Let us add that both the simulators show the same data.

Creating a linear homogenous image from a circular photograph deformed by perspective could not have been easy. It is a deformation of the reality but a circular model would not be readable. Nevertheless, you will also find such model here later. Now let us at least bow to the author of the original idea and realization.

In our description of the calendarium, we will focus at the displayed information of the calendar dial. The outer appearance can be found in the photogallery.

Along the perimeter of the calendar plate, there is an annulus divided into 365 “lines”, each consisting of four sections. For each day, the day within month, letter of the day within week, name of the saint and a syllable of the Cisiojanus are written in the direction from the inside. The specific current “line” is indicated by a new pointer (made during the repair in 1866) in the upper part of the calendarium. Initially, the current datum was indicated by a sculpture of an angel at the position of the 9th hour, which was certainly better readable. The main reason for the change was probably a desire to display the current month at the top in the upright position.

Simultaneous indication of the day within month and day within week by one pointer is resolved by means of an ingenious trick. There are no specific days written on the calendarium but only a recurrent sequence from a to g. The day indicated by a specific letter is derived from the proclaimed dominical letter.

(Only the dial can be set. The time cannot be turned back even with the help of Master Hanuš.)

Text: Petr Král, Java script: Vlasta Filler, Petr Král, photo: Vlasta Fillerr