first calender?

Question

when did humans start recording time dates n such
how old is the earth that we can be sure of

Answer 1

That is one of the greatest questions of all time. Nobody knows the answer to this question. We are not sure of anything.

Answer 2

It depends what you call a calendar.

The Chinese found bones with markings on them that indicate cycles of eclipses and, in the Bamboo Annals, a description of a meteor shower. The oldest confirmed description is from the year we call 2133 BC (that would make it 4139 years ago this past summer).

The Mayan Calendar has a "correlation date" of 11 August 3113 BC (in our modern system); however, it does not mean that the calendar existed that far back. The one that is most popular now (because a Long Count ends in 2012) could have been established well after that.

Adjusting calendars to past events is nothing new. The Romans did it. Even our present Anno Domini calendar was calculated in the 6th century and really became extensively used in the 9th century. If you are a purist, there was no such dates as AD 450 because the AD calendar did not exist yet. (But then, the BC calendar never existed...).

Star maps from the Babylonians were also found and they indicate the relative position of the Sun and planets for given times (making them useful as calendars). Were they calendars? If not, then one would have needed a calendar to use them properly. So we conclude that calendars existed, even though we have not seen them (except if the star chart itself is a calendar).

A more "recent" example that is most probably a calendar is the Nebra disc (3600 years old), a Babylonian bronze disc. It was found in Germany, hinting that calendric information was already circulating.

The first stones of Stonehenge (in England) were erected around 3600 BC. Even if we still argue about the purpose of Stonehenge, it could definitely serve as a calendar; some of its stones were placed to determine precise dates in the year (e.g., solstices). This would make the oldest stones a calendar at least as old as the Hebrew calendar.

There is evidence that the site was used before the stones were erected (with traces of very old wooden posts, now rotted), as far back as 8000 BC. However, it is impossible to determine if the wooden posts could be used for calendric purposes. Because of the later use of the site, it is easy to suppose that they were, but we can't prove it. That would make the site a 10,000 year old calendar.

There are many other henges in what now forms the United Kingdom and most have been surveyed by Thom. However, they are not all easy to date. In some cases, the hypothesis is made that they serve as calendars and, from that supposition, a date is determined (because of precession, nutation and other "wobbles" of Earth's rotation axis, it may be possible to determine the era when things would be lined up and made to match the alignment of stones). Some are older than the "stone" part of Stonehenge, but none seem older than the wooden post remnants found at Stonehenge.

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The dating of Earth's age uses other types of "calendars". They are the markers of nuclear physics, not man-made calendars.

Here is one example. There are many.
Uranium is radioactive. Each isotope of Uranium decays to a different isotope of lead and it does so at a different rate. For example, Uranium 238 has a half-life of 4.46 billion years. After that time, half of the original U-238 has become lead-206.
Uranium-235 (as long as the density keeps it below criticality) has a half-life of "only" 704 million years. After 4.5 billion years, 88% of it has decayed to lead (but not lead-206).
Uranium deposits on Earth are always found with contents of lead, with a specific mixture of isotopes that correspond to the decay of the various isotopes of Uranium.

It is supposed that, at some point at the start, some Uranium existed in a pure state. Some may have been mixed with lead at the start, but there are no chemical reasons why all uranium would have been mixed with lead.

Based on the isotope mixtures of lead mixed with uranium (also of its measured isotope mix), and using our knowledge of the rate of decay of the various isotopes of uranium, it is possible to estimate how long the uranium must have been there in order to explain the lead isotope mixture.

But that is more of a "chronometer" than a calendar.

Answer 3

Every time an archaeologist unearths evidence of astronomical observations, it is automatically the "world's oldest calendar". That's because they rely on publicity to propel their fund drives.

There are probably some primitive calendars hidden among 6000 to 8000 year-old petroglyphs, but no one has recognized what they are.

Check the following links and take your pick.

The Earth is about 4,500,000,000 years old. We know that because Mother nature left her own calendar for us to read, as soon as we got smart enough to read it.

Answer 4

The Hebrew (or Jewish) calendar is the oldest - the Hebrew calendar's epoch (reference date) is equivalent to Monday, October 7, 3761 BCE in the Julian calendar. That makes it almost 5800 years old.

The Earth itself is much older. Modern geologists consider the age of the Earth to be around 4.54 billion years .
This age was determined by combining the interpretations of oldest-known terrestrial minerals (small crystals of zircon from the Jack Hills of Western Australia) and astronomers' and planetologists' determinations of the age of the solar system based partly on radiometric age-dating of meteorite material and lunar samples.

Answer 5

the earliest we have on record, is the mayan calender, which as of today still remains the most accurate method of recording time. how they did it is a mystery ...