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AMONG MY many ornamental objects of questionable modern utility is a perpetual calendar. After all, there’s always the Calendar icon on my smart phone. Also, complete data are displayed, to the minute, on my computer screen. Nevertheless, I own a perpetual calendar that’s good for 40 years, 1943 through 1982.
A little research uncovered more timely devices calendaring today’s dates and good for 40 years, 50 years or 100 years. This got me thinking about how such calendars work.
My perpetual calendar was acquired from an antique store in Hungerford, nr. Newbury, Berks., England. Inscriptions read, “V·E DAY—May 8th 1945” and “V·J DAY—Aug. 15th 1945.” It’s heavy, looks like steel, but is non-magnetic. Wife Dottie is confident it doesn’t look like brass, even after more than 70 years; and I’m confident of her expertise.
I tried researching its patent number, but to no avail. One U.S. Patent No. 10,055 is for preparing paraffine-oil, 1853; another (?) No. 10,055 is for a gig saddle, 1882. British Patent No. 10,055 is an improved method of packing eggs for shipment, 1893.
In operation, the upper window of my calendar rotates to show years from 1943 through 1982, to be aligned with months arranged in the odd pattern of January/October; May; August/February (in red); March/February/November; June; December/September; and July/April/January (in red). Perform the appropriate alignment of year with month, and the bottom window shows days of the week with dates.
How does it know? And how come it works only for the years 1943 through 1982, not just “to 1982,” but why quibble?
I sure wish I knew. My research on the matter yielded only complexity, not resolution.
Notes Wikipedia, Algorithms: “Every four years, the starting weekday advances five days, so over a 28-year period it advances 35, returning to the same place in both the leap year progression and the starting weekday. This cycle completes three times in 84 years, leaving 16 years in the fourth, incomplete cycle of the century.”
I believe I’ll just use my smart phone.
Our current calendar was introduced by Pope Gregory XIII in 1582. (By the way, chants are named after another Gregory entirely, Pope Gregory I, aka Saint Gregory the Great, c. 540 – 604.) The Gregorian calendar corrected an assumption of the earlier Julian Calendar that the year had 365 1/4 days, whereas it’s actually 10 hours 48 minutes less.
No big deal, you say? It was when Easter is off by 10 days, responds Pope Gregory XIII. Let’s just have Thursday, October 4, 1582, followed directly by Friday, October 15, 1582.
France, Italy, the Polish-Lithuanian Commonwealth, Portugal and Spain, being predominately Roman Catholic, adopted the Gregorian Calendar post-haste. Britain didn’t switch until 1752 (and didn’t that complicate international get-togethers).
Russia didn’t switch over until 1918 with its revolution; Greece, following the Orthodox faith, not until 1922. The difference, depending on year, varied from 10 days in the 17th century to today’s 13 days.
None of this, of course, affects my perpetual calendar, clearly a Gregorian device. But it still embodies our calendar’s complexity of months of 28, 29, 30 or 31 days, together with leap year rules.
VPCalendar.net gives a comparison of calendars, including the Baha’i, Coptic and Ethiopic, Gregorian, Hebrew, Islamic, Julian and Persian. Loosely, some of these are solar, some lunar, and one, the Hebrew, both. I’m curious to investigate the Baha’i and Coptic/Ethiopic calendars, because they have months as short as 4, 5 or 6 days. (Imagine getting jagged for a month’s rent.)
In any case, I can report on online sources for perpetual calendars. Ten Thousand Villages, a non-profit organization, was established in 1946 and specializes in encouraging artisan partners around the world to use environmentally friendly processes. It offers a 40-year calendar, 2010 to 2049, handmade in India in two-color brass.
And Amazon, the Everything Store, offers a Smithsonian 40-year Calendar and Magnifier. It’s brass-plated, with 2X magnification of its swing-out lens, and patterned after a device in the Home and Community Life Collections, National Museum of American History, Kenneth E. Behring Center, Washington, D.C.
I didn’t check on Christmas delivery. My 40-Year Calendar ends at December 31, 1982. It was a Friday. ds
© Dennis Simanaitis, SimanaitisSays.com, 2015