""Dinosaur Calendars" is a fanciful description of a number of possible prehistoric and future calendars based on evidence that tidal friction against the continents is gradually slowing the rotation rate of the earth (and causing the moon to receed from the earth). Also, fossil stromatolite corals show the number of days per year in their microscopic growth rings. The oldest reefs have 424 rings per year about 600 million years ago, with a gradually decreasing number of days to the present.
Six hundred million years ago, the moon was closer to the earth, the tides were higher, and the days were shorter. Paleozoic years were just as long as ours, but there were more days in the year. Stromatolite coral reefs had (then and now) a microscopic growth ring for each day of the year. The dominant animals were Trilobites, the earliest known members of Arthropoda, the group which now includes lobsters and insects.
A fossil Trilobite calendar has been found from the late Precambrian period, 600 million year ago. It has 424 days in a year, with 16 months which alternate between 26 and 27 days in length. As you can see, the Trilobites counted by fours, probably indicating that a single nerve served two pairs of appendages. According to analyses of gas bubbles trapped in amber, the atmospheric oxygen content was only about 2% instead of the present 21%, so Trilobites probably had a little trouble remembering what the date was.
Another Trilobite calendar found is about 500 million years old, from the late Cambrian period when there were 412 days in the year. This calendar divided the year into two 27 day months and fourteen 26 day months.
The first calendar we know of with thirty day months is a 390 day amphibian calendar from late Carboniferous times about 280 million years ago. The amphibians had a six day week, which means they had short weekends, or only had to work four days a week. With my luck I would have to work five and a half days each week. There were 13 identical 30-day months.
A dinosaur calendar from the Jurassic period about 170 million years ago has been found in Utah. It has 380 days and shows that dinosaurs had a five day week. The biggest problem with their calendar was the nineteen months, each named after one of those five-syllable monsters!
By late marsupial times 65 million years ago, early in the Paleocene epoch, there were 371 days in the year. The moon's pull on the tides and tidal friction on the earth were continually slowing the spinning earth. Where we might have used 53 seven day weeks, marsupials followed the Trilobite practice of alternating 26 and 27 day months - 14 of them. Marsupials didn't scratch in the mud like Trilobites. They left their calendars in the form of coprolite mounds, which we can't show in this family publication. (CENSORED)
The 366 day year could have ushered in the Age of Man, but we weren't ready yet. There were 366 days in the year ten million years ago when primates were entering the expanding grasslands of Africa. You have probably heard of the Julian calendar. Old Julias Cro Magnon could have invented the Julian Calendar, because there were 365 1/4 days in the year 10,000 years ago. Julius Caesar was even late for the Gregorian correction. They should have started dropping three leap year days every 400 years back in 1900 B.C. In 28,000 years our descendants or successors will have to delete leap year every century year. Leap year will completely disappear in about three million years, when there will be exactly 365 days per year.
Our basic 12 month 30 day calendar can be used far into the future just by adding or subtracting a few days a year. By 110 million years from now, the penguins will be ready for something different. A 355 day year could have 5 seasons with 71 days in each season. The seasons could be grouped in 5 twelve day weeks and one eleven day week. The more sophisticated civilizations in the Penguin II Age will probably have several calendars. 350 days could be divided into 14 months of 25 days or 10 months of 35 days. Some penguins will probably demand a compromise of 12 months with 30 days (which is 360 days!) Others will romantically cling to lunar calendars.
By Penguin III times, citizens will be ready for the old Dinosaur Calendar's five day week. If they use a three week month, they will need 23 months a year. They could name them after all their predecessors on the planet, but they will probably name them after generals, popes, and numbers like 7, 8, 9, etc. Will the aliens (230 million years from now) laugh at a 23 month calendar? I doubt it -- they have probably seen all these and more!
By the time of the Billennium, a billion years from now, the earth will have slowed to 310 revolutions per year. There will be only 11 lunar months per solar year. Muslim years (12 lunar months) will be longer than solar years, rather than shorter as they are now. By our second billennium, we may be ready for silicon-based life. The moon will be 290,000 miles away and show only 10 cycles of phase changes per year. By the Googlennium, ten to the one hundredth power years from now, matter itself will fall apart and black holes evaporate, until there are only electrons, positrons, neutrinos and photons skittering across space.
SUMMARY OF POSSIBLE CALENDARS
Million
Days per
Years "AGE"
year Calendar
# days
PAST
4500 Lunar collision
4380 Asteroid
4380
600 Precambrian
424 Trilobite I 8x27+8x26
500 Cambrian
412 Trilobite II 2x27+14x26
280 Carboniferous
390 Amphibian
13x30
170 Jurassic
380 Utah Dinosaur 19x20
65
Paleocene
371 Marsupial
7x26+7x27
10
Miocene
366 Primates
6x30+6x31
PRESENT Gregorian
365.2425 1900 B.C. to 28,500 A.D.
FUTURE
3
Saharan
365 Excess CO2 causes deserts
55
Antarctic
360 Antarctica moves north
110 Penguin
I
355 Penguins spread
5x71
165 Penguin
II 350
Penguins dominate 14x25
230 Penguin
III 345
Extraterrestrial contact
1000 Billennium
310 Solar Power
10x31
2000 Billennium
II 280
Silicon-based life 10x28
1014 years Star Death
All stars burned out
1040 years Proton Death
All protons fallen apart
10100 years Googlennium
All black holes evaporate