|
 In
the year 45 BC, a powerful man instituted a reform that
would have
a major impact on the advancement of civilisation. The man
was Julius Caesar, and he had decided to change a Roman
calendar that was woefully inaccurate. The calendar used at
that stage was adjusted at the whim of the pontiffs (priests), who would often have
hidden agendas and concerns
other than accuracy. Farmers had to
cope with a calendar where winter months could change to
summer months within a period of a few years.
Understandably, crop failures were a common result.
Had Julius Caesar not been so
powerful, he probably would not have been able to get his
calendar reforms past the establishment (the senate had
appointed him as consul and dictator). Against subdued
resistance from religious circles, he instituted the new
calendar (currently known as the Julian Calendar). It
covered all dates from January 1, 4713 BCE (before common
era). For the first time there was a calendar that
corresponded with the lunar and solar cycles and farmers could rely on
it to determine when to sow crops.
It was a calendar based on astronomical observation and the
calculated time the earth took to cycle once around the sun.
It had 365¼ days and a leap year every four years, to
compensate for the ¼ day.
As a testament to its accuracy, the Julian Calendar remained in use
unchanged, for over 1 500 years.
 By
1582, however,
the calendar was incorrect by 10 days. Under the instruction of Pope Gregory XIII, the
calendar
was changed by dropping the leap year at every turn of the
century, except where the century is divisible by 400. He
also adjusted the date by deleting the 10 days that the
calendar was in error. This resulted in the good citizens
going to bed on Thursday, 4 October 1582, and waking up on
Friday, 15 October 1582. Many people thought that this was
sacrilege and there was widespread
discontent (mostly superstitious) about the changes. Several
non-Catholic countries only adopted the so-called Gregorian
Calendar two centuries later.
Since the Middle Ages scholars have strived to convert the
calendar into an understandable mathematical equation that
can apply to any date in the past or future (perpetual
calendar). In 1882 a reverend by the name of Christian
Zeller (1822 - 1899), a protestant minister in Markgröningen
(20 km NW of Stuttgart) came the closest to simplifying a
formula for a perpetual calendar, and his algorithm is named
the Zeller Congruence. His algorithm is complicated and only
comprehensible for mathematicians, though. An example of his
equation is given below:
In 1991, South African
Etienne A. Marais developed a 12-digit calendar key that
enabled any layman to calculate a perpetual calendar, using
simple arithmetic. The technique, called the Marais Formula,
is fully described on the
Formula - page.
Interesting Facts:
* The year 46 BC had 455 days and is known as the last
of the "Years of Confusion".
* The actual time the earth takes to revolve around the sun
is 365.24219 days, so the Julian Calendar only had an error
margin of 0.00781 days per year (approx. 11 minutes 25
seconds, or one day every 128 years).
* The Gregorian Calendar has an error margin of one day
every 3 300 years.
* Russia only switched to the Gregorian Calendar after the
"October Revolution" of 1917. The revolution actually
happened on 7 November 1917, and not the celebrated 25
October 1917. |