Abstract: The secular perpetual calendar comprises an additional mechanism (4 to 13) integrated in a conventional perpetual calendar mechanism comprising a last wheel (13) making one revolution in 400 years, this wheel (13) carrying a cam (13?) of which the steps cooperate with a lever (9) on which pivots a wheel (6) which carries a satellite (7?) on which is attached the February cam (7) and the cam (13?), which makes one quarter turn every century, presenting three low steps enabling the lever (9) to move back in such a way that the cam (7) on which the multiple lever (2) will press is in the same position as for a conventional 28-day month of February three times in succession for the years 2100, 2200 and 2300, and then a high step to restore the 29th of February of the year 2400.