Contact: David K. Clarke – ©
In the United Kingdom and Australia dates are usually written: day, month, year; for example today's date is:
I believe that in China and Japan they write: year, month, day; eg.
The USA has the most foolish system, they write: month, day, year; eg.
The most significant digit (the one that indicates thousands) comes first, the next most significant digit (indicating hundreds) comes next, etc. So, following the same arrangement, it is logical to place the year first, the month second, and the day last. This system is increasingly being used in computer applications. If dates written in this format are put through an alpha-numeric sorting process they come out in chronological order.
I have used this way of writing dates widely in my pages.
A rational way of writing the dateThe oriental system for writing dates, then, is the only one that is logical. For example, the date '1986/12/26'. Starting from the left:
Date and TimeExtending the logic one step further, you could add numbers to indicate the time of day. For example, the date and time on your computer clock when you loaded this page was: (year/month/day hour:minute:second).
By the way, your time zone offset, as set on your computer, is hours. To convert to Universal time (Greenwich mean time), your time.
(-:Metric Time :-)Of course, to be completely rational, we should abolish all the strange month lengths, seven days in a week, 24 hours in a day, 60 minutes in an hour and have a completely metric time system. It could be based either on a standard second or perhaps on a year. We already have milliseconds and microseconds, we could have kiloseconds (about 17 minutes), megaseconds (about 12 days), gigaseconds (about 32 years – I am near enough 2Gsec old as I write this [2009/04/03]); or milliyears (about 9 hours), microyears (about 32 seconds), kiloyears (millenia), megayears and gigayears (the earth is about 4.5 gigayears old).
The length of a day (one complete rotation of the earth on its axis and relative to the Sun [a rotation relative to the stars is about four minutes quicker]) varies, so is not well suited as a unit of time. The day is getting steadily longer (due to the gravitational effects of Moon and Sun) and changes also due to the relationship between water/snow being stored at different altitudes and the conservation of angular momentum. For example, heavy snow falls in the Himalayas places increased mass at a point further from the centre of the Earth and slows the planet's rotation; the melting of mountain glaciers due to climate change would be causing the planet to rotate a very little faster.
Astronomer's time, Julian DayIn spite of the above spiel on the variability of the length of a day, astronomers use a form of date based on the day, called the Julian Day. According to this calendar, each new Julian day begins at Greenwich mean noon (because the astronomers who developed the system wanted the whole night to have the same day number; it's easier for them). Note that the Julian day (proposed by Joseph Justus Scaliger in 1583, and named for his father, Julius Caesar Scaliger) has nothing to do with the Julian calendar (named for that other Julius, Caesar).
If my calculations and your computer clock are correct, the Julian Day number at the time you loaded this page, was
Don't ask me why Joe decided to start his calendar on January 1st 4713BC, although it was probably an early enough date so that all known astronomical records would have positive Julian dates.