December 15, 1995
Lost, yesterday, somewhere between sunrise and sunset, two golden hours, each set with sixty diamond minutes. No reward is offered for they are gone forever.
Horace Mann (1796-1859)
We measure time in seconds, minutes, hours, days, weeks, months, and years.
The day is the time it takes the Earth to make one turn on its axis. A day is arbitrarily divided into 24 hours; each hour is divided into 60 minutes and each minute into 60 seconds. That is pretty straight forward.
The 7 day week is arbitrary and bears no real relationship to anything astronomical. The Jews got it from the Babylonians. The Romans associated the magical number 7 with the 7 moveable heavenly bodies: the Sun(Sun's day,Sunday), Moon(Moon's day, Lundi, Monday), Mars(Martis day, Mardi, Tiw's day, Tuesday), Mercury(Mercurii day, Mercredi, Woden's day), Jupiter (Jovis day, Jeudi, Thor's day, Thursday), Venus(Veneris day, Vendredi, Frigg's day, Friday), Saturn (Saturni day, Samedi,Saeturnisdaeg, Saturday).
The months were originally related to the cycles of the moon. The Hebrew calendar is a lunar one. The lunar month takes about 29.53 days, so a calendar based on the Moon has to be corrected frequently if the year is to correspond to the Earth's relationship to the Sun, and to the seasons.
A year is based on the time it takes for the Earth to make one turn around the Sun. The solar year takes 365.2422 days. Obviously, making months and years agree, and making years conform to the seasons takes quite a bit of finagling.
One of the reasons that many people are confused by the calendar is because it is a mixture of science, religion and politics. Yes, politics; the reason that some months have more days that others is in part because a few Roman emperors didn't want to be short changed in their month.
Nowadays time can be measured with great precision; much greater precision than any of us need in our lives. The small variations in time are corrected by adding an occasional second (a leap second) to a day. It is possible to predict centuries ahead at what exact time the star Sirius will appear on the horizon on any particular day.
Even with this precision, there is still one source of confusion caused by a monk in about AD 525 who suggested that years be counted from the birth of Christ. This was adopted throughout the Christian world. One of the reasons that religion got into the act was because the Catholic holidays are determined by the phases of the Moon. Among the problems are: Is the date 105 A.D. in the first or second century? How come time goes backwards if you go back before the birth of Christ? In a world where more than half the population is not Christian, how come the birth of Christ is used as a reference point? I usually dodge the issue of what century 1776 is in by referring to the seventeen hundreds instead of the century.
The fact that one revolution of the Earth around the Sun is not an even number has now been taken care of by adding a leap second every now and then to bring the calendar into sync with the Sun's behavior. In other words, on any day of any year, the position of the Sun and the other stars will be the same from one year to the next. So will the solstices and equinoxes. It will never again be necessary to bring the calendar in conformity with the realities of astronomy, as when the church added 11 days to the calendar. With these modifications, The Gregorian calendar(named for Pope Gregory XIII, even though astronomer Christopher Calvius did the work) works very well.
That still leaves us with the AD and BC business. Recently, geoscientist Cesare Emiliani has proposed reforming that, making the calendar a sensible scientific thing. He proposes starting the calendar at what is now called 10,000 B.C. That date would be the year one. It is the approximate time of the beginning of the Holocene epoch, which marks the end of the last ice age and the beginning of agriculture. With this modification, this year would be 11,995; or as it would be abbreviated, 1995. Jesus's birth would be the year 10,000. Jericho would have been founded in 3,001. To find out how long ago Jericho was founded, subtract 3,001 from 11,995. Emiliani also suggests that the year 12,001(2001) could be called the year 1 as a short cut.
I think that Emiliani's recommendations are excellent and that they would simplify the lives of many people in the future. No one would have to change anything of any consequence. For the vast majority of people, nothing would change. For a few of us, life would be simplified a bit.