The calendar measures astronomical time: Earth’s orbit around the Sun (Solar) and the Moon’s orbit around Earth (Lunar), or the Sun’s motions through its cycle prednisone 20mg dosage. It is more than a way to measure days, months or years.
Time, without a wristwatch or more modern techniques, measures larger units of time: days, part of day, season, month, astrological era, astronomical constellations and alignment of pole star.
Part of the confusion between cultures & religions is the variety and nature of calendars. Some calendars are ancient, some more modern, and some have tried in various ways to adjust to changes in Earth’s orbit and alignment.
Even the simplest time-keeping device, such as a sundial,
determines time by the size and angle of shadow derived from the angle of the Sun. The shadow is known to change with time of day, and again with the season. Using a sundial is inexact, requiring knowledge of the seasons to properly determine the length of a day.
The origin and necessity of a calendar or other time keeping devices is known to exist fully intact from Egypt, Babylon, and Sumeria, many thousands of years B.C.E. Civilization was already well formed by then.
Historically, the more ancient calendars were luni-solar. Today’s Western business calendar is purely Solar, while the Muslim calendar is purely Lunar.
Earth currently takes 365.25 days to complete one orbit around the Sun, which is called a year. The Moon takes 354 days. This is just over 11 days difference, which must be adjusted for to keep the two cycles (and the measurement of seasons) in balance.
This is why some calendars, such as the Jewish, Chinese or Indian calendars, have holidays on different days each year (according to the Western calendar, anyway.)
Solar Year
Ancient references are fascinating because of the different lengths of the year mentioned. Babylon had 360 days (12 months of 30 days). The apocryphal Book of Enoch speaks of the year having 360 days. Egypt had 365 (an extra 5 days between years). And today, we have roughly 365.254 days per year.
We can beleive one of two things:
1) that the ancients didn’t know how to measure a year accurately.
or
2) Earth’s orbit has shifted over time.
It may be easier to blame much on the supossed stupidity of the ancients, but the evidence doesn’t seem reasonable. If these people, the on’es who built the pyraminds, Stonehenge, Nazca Lines, and wrote detailed medical information can’t watch a planet move above them accurately, something is really wrong.
This leaves the unusual conclusion that Earth’s orbit shifted over time. We have witnessed great events that shifted our orbit several times in the last few years. According to the NASA website, it is said that “in theory, anything that redistributes Earth’s mass will change Earth’s rotation.”
The calculations also show the Japan quake should have shifted the position of Earth’s figure axis (the axis about which Earth’s mass is balanced) by about 17 centimeters (6.5 inches), towards 133 degrees east longitude.. This shift in Earth’s figure axis will cause Earth to wobble a bit differently as it rotates…In comparison, following last year’s magnitude 8.8 earthquake in Chile, Gross estimated the Chile quake should have shortened the length of day by about 1.26 microseconds and shifted Earth’s figure axis by about 8 centimeters (3 inches). A similar calculation performed after the 2004 magnitude 9.1 Sumatran earthquake revealed it should have shortened the length of day by 6.8 microseconds and shifted Earth’s figure axis by about 7 centimeters, or 2.76 inches.”
Over great spans of time, with similar large events, it is reasonable that Earth’s orbit has changed from a perfect 360 degree circle orbit to the eliptical 365.25 year we now have.
Matching Solar & Lunar Time
Different nations have their own specific means of making the length of the Solar and Lunar years remain reasonable coherent. This usually means adding an extra month to the end of the year every 7 years out of 19, in the same way a Leap Year adds one day every 4 to the end of February.
The two calendars are not perfectly aligned all the time, but overall the lengths of both the solar and lunar years match.
Calendar Measurement
The use of a calendar to determine time can be broken down into the types of units it measures:
Minute, Day, Month, Year, Age.
The oldest known calendars originated in Sumeria, then Egypt and Babylon. From there, came these, in order:
India
China
Roman/Greek
Julian
Gregorian
With our busy lives, measuring time has changed. From sundials and motions of Planets, we now receive our cell phone bills by the second, and scientists frequently measure milli, micro & nano seconds.
Time has become smaller as it speeds up.