naptar.lap.hu / Az időmérés kezdete

Celestial bodies, the sun, moon, planets, and stars have provided us a reference for measuring the passage of time throughout our existence. Ancient civilizations relied upon the apparent motion of these bodies through the sky to determine seasons, months, and years.

THE CALENDAR A calendar is a system of reckoning the time over extended intervals by combining days into longer groupings which are linked to the way in which we live. The groupings often have religious significance and some of the groups are linked to astronomical periods. Our calendar is made up of days, weeks, months and years. The day is the rotational period of the Earth; the week is a purely artificial period linked to the Biblical story of creation; the month is linked to the period of the Moon and the year is linked to the Earth's period of rotation around the Sun.

Az időről vallott általános európai felfogásra a görög filozófiai gondolkodás nyomta rá a bélyegét, amely annak múlását a térbeli mozgás képzetével hozta összefüggésbe. Az arisztoteliánus hagyományokon pallérozott európai elmék számára a tér valami olyasmi, mint egy hatalmas tartály, amely minden dolgot magában foglal, rendez és egybetart; ennek szűkebb-tágabb korlátai között élünk, ebben valósítjuk meg céljainkat születéstől az elmúlásig. A görög hagyományoknál jóval régebbi írásos tradícióra támaszkodó zsidó gondolkodás viszont az időt tartja valami hasonló dolognak. Számára ez az a „tartály”, amely magában őrzi az élet eseményeit, a születéstől kezdve a halálig. Erre a különbségre már a francia filozófus, Henri Bergson is felhívta a figyelmet, aki szerint a héber időszemlélet olyan, mint amikor zenehallgatás közben hallunk egy dallamot, amely fizikai időfogalmaink szerint elmúlt, de emlékezetünkben mégis elevenen él, és a folytatódó dallamsorral együtt áll össze egységes zeneművé.

Between AD326 and AD1582, Christianity determined Easter using an algorithm approved by a Church Council in AD325, with the equinox defined as March 21. From AD1054 (when the Orthodox and Catholic Churches split) through AD1582 both the Catholic and Orthodox Churches celebrated Easter on the same date, still using the algorithm from AD325. The Julian Calendar was used by the European (and Christan) communities until the Gregorian reform of 1582. Since AD1582 October (when the Gregorian Calendar was adopted by much of Catholic Europe), the Orthodox Easter usually falls on dates different than the Western Christian Easter, although apparently the Churches are discussing using the same formula to determine Easter - probably a formula different than that currently used by either Church. The Orthodox Easter is determined in the Julian Calendar. It has been claimed that Orthodox Easter does not fall on the date of Passover (15 Nisan in the Hebrew Calendar), or before it; this is true recently, but using the modern formulae for determining the date of Passover (rules which go back to the fourth century A.D.), one finds that, in fact, Easter occurred on the first day of Passover several times before the year A.D. 1000. From 1900 until 2099 the Eastern Easter will fall one (45.5%), four (4.5%), or five (21.5%) weeks after the Western Easter - and on the same date in 57 (28.5%) of those years. (I've compiled some Tables showing the offsets between Orthodox and Western Easters from 1583 through 3000 that shows this information.)

The Calendar FAQ includes a number of formulas for calculating various calendar values. I have written a very simple implementation of these formulas in the C language. Rather than providing the most efficient code, the implementation intentionally follows the formulas very closely.

Some notes about this article This document is meant as a "welcome" to the newsgroup rec.collecting.postal-history ("r.c.p-h") proposed by Bob Track, Mass. USA. The newsgroup "r.c.p-h" became active 17 November 1995 (Gregorian time ;-) and on the same day I uploaded the first version of this page. This document is a translation into English of a part of an article I wrote in 1985 about The Danish Perpetual Calendar and I myself find it indispensable in my study of Danish Postal History. Since 1995 this document has changed quite a bit thanks to a great response from many, many readers who have put their fingerprint on it: suggestions for changes, corrections, additions and new information. Thanks to all of you!

Aztec Calendar Babylonian Calendar Calendar Chinese Calendar Egyptian Calendar Epact French Revolutionary Calendar Friday the Thirteenth Golden Number Gregorian Calendar Hebrew Calendar Hindu Calendar Iranian Calendar Islamic Calendar Julian Calendar Julian Date Leap Day Leap Year Mayan Calendar Modified Julian Date Roman Calendar

Prehistoric man, by simple observation of the stars, changes in the seasons, day and night began to come up with very primitive methods of measuring time. This was necessary for planning nomadic activity, farming, sacred feasts, etc.. The earliest time measurement devices before clocks and watches were the sundial, hourglass and water clock

The following article is adapted from a longer series of posts that I originally wrote for the Historical Writing section of Compuserve's Literary Forum in 1996. (The Literary Forum still exists under the name "Books and Writers Community", but its structure has radically changed, so most of the old sections are defunct.) I wrote the original in response to a skeptic (that's the polite word) who proposed the theory that conventional historians had grossly mistaken the chronology of both the ancient world and the Middle Ages. In the original piece, I tried to explain how historians piece together different facts to arrive at a chronology. Along the way, I described different historical calendars and the origin of the western calendar. In the following, I have extracted that portion of the earlier article that bears on the origins and history of the western calendar.

The purpose of the calendar is to reckon past or future time, to show how many days until a certain event takes place—the harvest or a religious festival—or how long since something important happened. The earliest calendars must have been strongly influenced by the geographical location of the people who made them. In colder countries, the concept of the year was determined by the seasons, specifically by the end of winter. But in warmer countries, where the seasons are less pronounced, the Moon became the basic unit for time reckoning; an old Jewish book says that “the Moon was created for the counting of the days.” Most of the oldest calendars were lunar calendars, based on the time interval from one new moon to the next—a so-called lunation. But even in a warm climate there are annual events that pay no attention to the phases of the Moon. In some areas it was a rainy season; in Egypt it was the annual flooding of the Nile River. The calendar had to account for these yearly events as well.

The Egyptians were the first people who created a twenty-four hour day. Time was a little bit different in those days. The night was divided up into twelve hours, which were designated by the position of stars in the sky. The day was divided into ten hours and a shadow clock was used to keep track of these hours. The twilight hours were the hours before dawn and after sunset. The Egyptians thought they were the first to invent the shadow clock, but they were mistaken. At the same time, the Chinese, Babylonians, Greeks and the Romans were using instruments to tell time. Sundials were used in some of these groups, not because they work better, just because that's how they decided to tell time.

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