an eighth edition was published in 1885. In 1864, he proposed a calendar reform for Russia: After dropping 12 days to align with Gregorian calendar dates before the year 1900, the leap year in 1900 along with every 128th year afterwards (2028, 2156, etc.) under the Julian rules would be cancelled. This would give a mean year of 365 days, 5 hours, 48 minutes, 45 seconds, which is extremely close to the mean tropical year. Neither the Tsar nor Orthodox clergy accepted this unsolicited proposal, though a modified version of it was made by Sergey Glazenap in 1900, and ultimately Russia would adopt the Gregorian calendar in 1918. The craters Mädler on the Moon and Mädler on Mars are both named in his honor. References Bibliography Heino Eelsalu, Dieter B. Herrmann: Johann Heinrich Mädler (1794–1874): Eine dokumentarische Biographie. Akademie-Verlag Berlin, 1985 ISSN 0138-4600 (German) External links Frank J. Tipler, "Olbers's Paradox, the Beginning of Creation, and Johann Mädler," Journal for the History of Astronomy, Vol. 19, Pt. 1 (February 1988), pp. 45–48. F. J. Tipler, "Johann Mädler's Resolution of Olbers' Paradox," Quarterly Journal of the Royal Astronomical Society, Vol. 29, No. 3 (September 1988), pp. 313–325. Frank J. Tipler, "More on Olbers's Paradox," a review of Edward Harrison, Darkness at Night: A Riddle of the Universe (Cambridge, Mass.: Harvard University Press, 1987), Journal for the History of Astronomy, Vol. 19, Pt. 4 (November 1988), pp. 284–286. (Note that the last page is missing in the PDF version of the article at the foregoing link, but is contained in the GIF version.) http://www.uapress.arizona.edu/onlinebks/mars/chap04.htm http://www.obs.ee/obs/maedler/maedler.html Obituary MNRAS 35 (1875) 171 1794 births 1874 deaths 19th-century German astronomers Selenographers Historians of astronomy Recipients of the Lalande Prize