S. Khalid Shaukat
Ancient Calendars: All
ancient calendars were lunar calendars. The practice of starting a month at the
first sighting of a new moon was observed not only by Romans but by Celts and
Germans in
When human civilization excelled in agriculture, there was
a need for having a calendar that repeats the seasons so that it would help
sowing and harvesting on repeated calendar dates. This calendar was established
based on rotation of the earth around the sun. Early
estimates of this rotation was 360 days, so the first solar calendar was
invented having 12 months of 30 days each. Some civilizations invented a
lunisolar calendar which basically had lunar months based on new crescent moons
but were adding days or a month to be decided by priests/rabiis wherever and
whenever they felt to satisfy social and religious needs to keep their calendar
in phase with seasons. This practice of adding days or a 13th month was called
"Intercalation".
Babylonian Calendar: Around
1800 B.C. Babylonians were using strictly lunar calendar based on the visible
new crescent but somewhere between 1100 B.C and 800 B.C. a lunisolar calendar
was adopted using intercalation which was haphazard. Some sources report that
during the reign of the Babylonian king Nebuchadenezzar II (630 B.C. - 562
B.C.) priest/experts discontinued their practice of looking for the new moon
and adopted a 365 day calendar of 12 months of 30 days each, with five days
added at the end of the year.
Hindu Calendar: Hindus have both solar and lunisolar calendars. In the
Hindu solar calendar month is 30 or 31 days and begins on the day of first
sunrise after the calculated time of the mean sun's entry into the next
zodiacal sign. If the calculated time is after
Chinese Calendar: Chinese also started using a lunisolar calendar with
months beginning on the day of the new moon. Years contain 12 or 13 such months , with the number of months determined by the number
of new moons between successive winter solstices. There have been more than 50
calendar reforms since its inception in the 14th century B.C.
Egyptian Calendar: In
order to device a solar calendar in ancient times experts observed that Sirius,
brightest of all the fixed stars, appeared in summer, rising above horizon just
before sunrise. They also noticed that Sirius would return to its position
after 365 days. Thus, Egyptians deviced a solar calendar built around 365 days.
They gave up their practice of looking for the new moon in favor of the solar
calendar.
Greek Calendar: By
13th century B.C. Greeks were using lunar calendar based on the visible new
crescent. Later they also learnt intercalation to bring lunar calendar in phase
with seasons and started using lunisolar calendar. Astronomers such as Maton in
432 B.C. calculated a 19-year lunisolar cycle where moon phases would repeat in
the same seasons. This was called "Metonic Cycle" where 19 solar
years were equal to lunar 19 years and 7 months. This concept was later adopted
by Jewish or Hebrew calendar.
Hebrew Calendar:
Hebrew Calendar, promulgated by the Patriarch, Hillel II, in the mid-fourth
century is a lunisolar calndar with months based on new crescent moon but
adding a 13th month every so often to bring their lunisolar calendar in phase
with the seasons. It consists of 12 month in a common year and 13 months in a
leap year. Leap years occur seven times in a cycle of 19 years (Metonic cycle), such that 3rd, 6th, 8th, 11th, 14th, 17th, and 19th year
are leap years. Common years may have 353-355 days, while leap years may have
383-385 days. The beginning of the Hebrew new year is
determined by the occurrence of the new moon (conjunction) of the seventh month
(Tishri), subject to possible postponement of a day or two according to some
rules.
Roman Calendar: About seven hundred years before Julius Caeser, Romans
were observing some nominally lunar calendar, and were adding days or a 13th
month at the end of their calendar year to keep their calendar in phase with
seasons.
|
Roman Calendar before 47 B.C. [Used Intercalation of days
or a 13th month] |
||||||||||||
|
Number |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
11 |
12 |
|
Month |
Martius |
Aprilius |
Maius |
Junius |
Quintilis |
Sextilis |
September |
October |
November |
December |
Januarius |
Februarius |
|
Days |
29 or 30 |
29 or 30 |
29 or 30 |
29 or 30 |
29 or 30 |
29 or 30 |
29 or 30 |
29 or 30 |
29 or 30 |
29 or 30 |
29 or 30 |
29 or 30 |
The new year
used to begin on March 15, which was the date when new consul took office. In
153 B.C. the beginning of the year was changed to January 1. This was carried
over into the Julian calendar.
Julian Calendar: Following his conquest of
By the year 46 B.C. it was noticed that the spring equinox
had shifted by about 2 months coming in May. Caeser wanted to bring spring
equinox into correct position of Martius (March) 21. The year 46 B.C. is
regarded as the "year of confusion" by modern authors, because in
that year two intercalations were done; one to correct for spring equinox and
the other to change lunisolar calendar to purely solar calendar resulting in
the length of that year to 445 days. The following year i.e., 45 B.C. the
Julian Calendar looked like this:
|
Julian Calendar (of Julius Caeser), 45 B.C. onwards |
||||||||||||
|
Number |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
11 |
12 |
|
Month |
January |
February |
March |
April |
May |
June |
Quintilis |
Sextilis |
September |
October |
November |
December |
|
Days |
31 |
30(Leap) 29(Non-leap) |
31 |
30 |
31 |
30 |
31 |
30 |
31 |
30 |
31 |
30 |
Caeser was assassinated in 44 B.C. and the month Quintilis
was later renamed as Julius (July) to honor him. Soon after Caesar's
assassination, his nephew and adopted son Octavian became the emperor that we
refer to as "Augustus," an honorary title that had been bestowed upon
him. For a time after his death, priests in charge of the calendar erroneously
inserted an extra day every three years instead of every four. As a result,
this caused the calendar to again drift away from the seasons, an error that
needed correction. In 8 A.D. Octavian found it necessary to readjust the
calendar. To eliminate the effect of this extra intercalation, leap years were
discontinued from about 9 B.C. until 8AD. The leap years were:
45BC, 42BC, 39BC, 36BC, 33BC, 30BC, 27BC, 24BC, 21BC, 18BC,
15BC, 12BC, 9BC, 8AD, 12AD and every 4th year from then on.
To reward him for his accomplishments, the Roman Senate
voted to name a month in his honor, just as the month of Quintilis had
previously been named Julius (July) after the first Caesar. Because Octavian
had been born in Septembris, they offered to rename that month for him. He
chose Sextilis instead, because several times he had been fortunate during that
month. But the way the story goes, Sextilis in Octavian's time had only 30
days. Octavian's advisors suggested that the month named after him should not
be deficient compared to Julius's month of 31 days. Octavian (Augustus) thus
looked around for a month from which he could remove a day. Romans had religious
festivals that were held on specific days of each month; it would have been
difficult for him to delete any day that remembered a revered event, so he took
a day from Februarius which was already an odd month and added it to Sextilis,
which was then renamed Augustus (August). So February now had only 28 days in
common years but had 29 in leap years.
If Octavian had made no further changes, July, August and
September, three consecutive months, would then all have had 31 days. In order
to prevent a string of three 31 day months in a row, he removed one day each
from September and November and added one day to both October and December. As
a result, there are now only two 31-day months in succession in the middle of
the year (July and August) and two at the turn of the year (December and
January). Others claim that lengthening the month of Sextilis and renaming it
Augustus was done not by Octavian but by the consuls Asinius Gallus and Marcius
Censorinus who served as Ordinary Consuls of the
|
Julian Calendar (of Augustus), 8 A.D. onwards |
||||||||||||
|
Number |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
11 |
12 |
|
Month |
January |
February |
March |
April |
May |
June |
July |
August |
September |
October |
November |
December |
|
Days |
31 |
29(Leap) 28(Non-leap) |
31 |
30 |
31 |
30 |
31 |
31 |
30 |
31 |
30 |
31 |
As time progressed, the church did not like the idea of
January 1 being the new year, and in 567 A.D. the
council of
Gregorian Calendar: The prevailing Julian calendar served well for a long
time. However, adding an extra day every four years resulted in extending the
calendar over eleven minutes beyond the seasons every year. This was not
perceived as a problem for hundreds of years, but by the middle of the
sixteenth century of this Common Era, these added minutes had accumulated to ten
days. As a result, religious festivals were being observed on the wrong date as
compared with their original seasons. This problem had been known and discussed
for several centuries, but was not completely corrected until near the end of
the sixteenth century (1582 A.D.) at the time of Pope Gregory XIII resulting in
present Gregorian Calendar. Pope Gregory XIII decreed that after
|
Gregorian Calendar, 1583 A.D. onwards [Only the leap year
treatment was modified] |
||||||||||||
|
Number |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
11 |
12 |
|
Month |
January |
February |
March |
April |
May |
June |
July |
August |
September |
October |
November |
December |
|
Days |
31 |
29(Leap) 28(Non-leap) |
31 |
30 |
31 |
30 |
31 |
31 |
30 |
31 |
30 |
31 |
This Gregorian correction was adopted by
Bibliography:
1. "Encyclopedia Britannica"
2. "Calendrical Calculations: The Millenium
Edition," Reingold, E.M., and Dershowitz, N.,
3. "Chronology of the Ancient World," Bickerman,
E.J.,
4. "Calendars," Doggett, L.E., University Science
Books,