The basics of the calendar.
Ø Types of calendars.
is a time division system in years, months, and days.
the astronomical phenomenon of reference, three types of calendars are
Solar calendars :
based on the cycle of the seasons, which is to say on the period of revolution
of the Earth around the sun.
The year has
365 days, divided in 12 months, but a periodic adjustment is necessary to take
into account the fact that the actual duration of the year of the seasons is
about 365.25 days.
primitive solar calendars (in Egypt in particular), the year often had only 360
days, and it was added 5 additional days.
Lunar calendar :
based on the cycle of phases of the moon. The year is divided into 12 months of
29 or 30 days alternately and counts 354 days or an entire number of lunar. The
gap of 11.25 days with the solar year causes very fast adrift of the months
through the seasons.
Lunisolar calendar :
the two precedents. The year counts 365 days, as in the solar calendars, but
the beginning and the end of the months are calculated so that it
coincidentally, as much as possible, with a moon.
Ø The division of time.
In all civilizations, the requirements of social life have led
to the measurement of time, to situate events passes, to foresee future
activities and to have a temporal reference system suitable to regulate the
From antiquity, the observation of nature allowed to identify three
astronomical phenomena that could be used to measure time: The alternation of
day and night, the phases of the moon and the seasons.
of time were thus imposed:
The day, linked to the rotation of the earth on
The month, linked to the movement of the Moon around
The year, linked to the movement of the Earth around
man created clocks that define and descendent small intervals, lasting less
than one day: hours, minutes and seconds.
The week. The week is a seven-day period,
which is found in all the great modern calendars. The Egyptians, the Chinese
and the Greeks counted first by decades. The Babylonians were the first to use
the week. In the west, his employment spread to the beginning of the Christian era
and was formally adopted in 327 by Emperor Constantine I.
represents the full number of days closest to the four phases of the moon. Its
use was reinforced by the virtues traditionally attributed to the number 7 and
by the association of the days with the seven wandering stars known in the antiquity
(the Moon-Mars, Mercury, Jupiter, Venus, Saturn, and the Sun); do not derive
the names of the days used in the different European languages.
centuries, which span a hundred years, are numbered from an origin called Era. The
1st century of the Christian era began on January 1 of the year 1 to be
completed on December 31 of the year 100. The 21st century extends from January
1, 2001 to December 31, 2100.
Eras. An era is
called the point of departure of each particular chronology and by extension the
historical period corresponding to this particular chronology.
ancient eras, one can cite: the era of the Olympics that begins with the first
Olympic Games (776 B.C.E); The era of Rome, which was established by Varro I
(B.C.E) and begins with the legendary foundation of Rome (753 B.C.E); The Era
Buddhist, which begins with the year of the Death of Buddha (544 B.C.E),
according to the Sinhalese tradition.
Christian era is dated the year following the birth of Christ. According to the
calculations made in 532 by the monk Denys the Little, Jesus was born on
December 25 of the year 753 in Rome. The following year is counted as the year
1 of the Christian era. In fact, Jesus was probably born four or five years
earlier. The Muslim Era is dated from the displacement of Muhammad in Medina,
the hegira (July 16, 622). The Judaic Era, established in the fourth century by
Rabbi Hillel, corresponds to the year of the creation of the World (3761 B.C.).
The Republican Era is dated the proclamation of the 1st French Republic (September
22, 1792). It remained in use until December 31, 1805.
Ø The beginning of
of the beginning of the year is purely arbitrary. In Gaul, the year set by the
Druids began the sixth night of the lunation (first quarter) following the
medieval West, the adoption of the Julian calendar did not mean that the year
began everywhere on the same day. In VI and VII century, the year was still
beginning on March 1 in several provinces. Under Pallab, she began Christmas in
the whole of the free Empire. Under the Capetian, the New Year’s Day coincides
with a feast of Easter: Almost general in the 12th and 13th centuries, this use
is still attested in the sixteenth century.
In some regions,
the year changed on March 25, the Annunciation feast. New Year’s gifts were
exchanged in early April. From there would come the custom of the ‘ ‘ April
fool’s day ”?
Charles IX made the date of January 1 compulsory as the origin of the year. In
Germany, this choice had been enacted around 1500. In Great Britain, the date
of March 25 was kept until 1751 inclusive. In Russia, until Peter the Great,
the year began on the September 1st; it then began on January 1 of the Julian
calendar (12, then January 13 of the Gregorian calendar) until the adoption of
the Gregorian calendar.
from 1793 to 1805, the year began legally on the day of the autumnal equinox,
the date of the proclamation of the Republic.
The old calendars.
Ø The Egyptian
Egypt, the civil calendar resulted from the combination of a primitive lunar
calendar and an Agrarian calendar, set on the Nile cure.
(kiosk) of the Xxx dynasty, on which are engraved the 36 periods of 10 days
that form the Egyptian year. (Louvre Museum, Paris).
were counted from the advent of the reigning pharaoh. The year counted 365
days: 12 months of 30 days and 5 additional days. The years were counted from
the advent of the reigning pharaoh: Akhet (The Flood), Peret (the exit of the
land out of the water = winter), Shomu (drought = summer). Designated by their
rank in the season (e.g., 3rd month of flooding), they were divided into three
Cure began at about the time the Sothis Star (Sirius) reappeared a little before sunrise.
This event marked the beginning of the year, the first day of the first month
of the flood.
Each day was
divided into 24 hours (12 for the day and 12 for the night).
Ø The Babylonian
it served as the basis for the Jewish calendar.
counted 12 months of 29 or 30 days. The onset of a new lunar crescent in the
sky marked the beginning of the month. The beginning of the year usually
coincided with the first lunation following the Spring Equinox. The gradual
shift between the lunar year and the year of the seasons was offset by the
periodic addition of a 13th month. The months of the Babylonian calendar were
named: Nisanu, Aru, Simanu, Dumuzu, Abu, Ululu, Tisritum, Samna, Kislimu,
Tebetum, Sabatu, and Adar. The names of the months of the Jewish calendar
derive from it.
began at sunset and was divided into twelve equal Beru, split into 60
double-minute, and each double-minute in 60 double-seconds.
Ø The Greek
first used a lunar calendar. From the life B.C.E. they tried to harmonize with
the seasons, but the adjustment
included 12 months of 30 days. Then the alternation of 30 days (full months)
and months of 29 days (cellar months) allowed a better agreement of the
calendar with the cycle of phases of the moon (year of 354 days). At the time
of Solon VI (B.C.E), we tried to adjust the calendar on the solar cycle; by
intercalary a 13th month every two years, but the year was now too long.
began at sunset. Day and night were divided into 12 equal hours, the duration
of which varied according to the seasons of 45 and 75 minutes. Ten days was a
Ø Mayan and Aztec calendars.
Among the Mayas, the succession of days was independent of Astronomical
They associated two calendars:
a ritual calendar of 260 days, the tzolkin; a solar calendar of
365 days, the Haab.
consisted of 20 periods of 13 days, designated by a particular name preceded by
a number from 1 to 13. In each period, the day preceded the number 1 had a
names of the days were: Ik, Akbal, Kan, Chicchan, Cimi, Manik, Lamat, Muluc,
Oc, Chuen, Eb, Ben, Ix, Men, Cib, Caban, Eznab, Cavac, Ahan, and Imix.
consisted of 18 months of 20 days and a harmful month of 5 days. Pop
was the first month of the year, and the first day of a month was wearing the
number 0: the day of the year was written so 0 pop.
calendars were employed together. The full date of one day included an
indication of the tzolkin followed that of the Haab: 2 Ik 0 Pop, then the day after
3 Akbal 1 Pop, and so forth. For long periods, the Maya used a system based on
multiples of the day, or Kin: 20 Kin = 1 uninal, 18 uninals = 1 tun = 360 days,
and so forth.
pictograms (glyphs) of the 20 days of the solar calendar appear on a
circular band surrounding a representation of the sun (in the center).
(National Museum of Anthropology, Mexico City).
Aztecs, the calendar was not
fundamentally different from the Mayan calendar. The ritual calendar called tonalpohualli
included 20 periods of 13 days. The solar calendar of 365 days was also similar
to that of the Maya, while probably not synchronous with him. It included 18
months of 20 days and 5 additional days called nemontemi, considered harmful.
Ø The Roman and
calendars are the origin of the calendar that we use today.
Roman calendar: The
primitive Roman year (year of Romulus) included 304 days and 10 months (4
months of 31 days and 6 months of 30 days). Under Numa Pompilius (7th century
BC.) or Traquin (life s. BC), the Romans adopted a lunar calendar: the year of
355 days is divided into 12 months that start at the new moon: Martius,
dedicated to Mars, Aprilis, dedicated to Aperta (Apollo), Maius, dedicated to
Maia, Junius, can be dedicated to Junius Brutus, Quintilian, Quintus, fifth
(now Julius in tribute to Julius Caesar), Sextilis ( sextus- sixth ) (became Augustus in honor of Emperor
Augustus), September (September – Seven), October (octo – eight), November
(novem – nine), December (decem- ten), Januarius ( dedicated to Janus),
Februarius (dedicated to Februrus).
this schedule to the seasons, the pontiffs add a cough two years an intercalary
month of 23 or 22 days, after 23 or 24 February, Mercedonius. This measure the
duration average of the year of the calendar 366 days. The Romans are still
unable to provide their year civil with seasons.
The Roman calendar was reformed by Jules Cesar, on the advice of the astronomer
Sogiene of Alexandria, in the year 708 of Rome (46 before note era). This solar
calendar is based on the assumption that the season’s year includes exactly
365, 25 days. The duration of the year known as leap years into account 366.
The extra day is added in the month of February, which is then the last month
of the year.
equinox is fixed at March 25, and the beginning of the year is reduced from
March 1st to January 1st, the date of inauguration of the consuls.
Religious and traditional calendars.
Ø The Christian
Christian ecclesiastical calendar is the Gregorian calendar, with fixed or
mobile religious festivals. The mobile festivities revolve around the Easter
feast, celebrated on the Sunday following the 14th night of the lunation
falling on March 21 or immediately thereafter. The date of Easter is therefore
between March 22 and April 25. But it can also be determined by a calculation conventional
(or comput), and thus establish it many years in advance.
elements of the compute: The compute comprises five elements: The Sunday letter, the
solar cycle, the Roman indication, the golden number and the epact. To
determine the date of Easter, you must know the Sunday letter and the golden
number of the Julian calendar, the Sunday letter and the epact of the Gregorian
v Sunday Letter:
Letter from A to G, the rank of which indicates Sundays in the calendar of the
year in question when letter A is issued on January 1, letter B to January 2 …
and so on to G for 7. In leap years, two Sunday letters must be considered: one
is valid until 29 February, the other for the following months.
v Solar cycle: The
rank of the year in question in a period of 28 years, after which the Sunday
letter repeats the same cycle of values.
v Indication: The
rank of the year in a 15-year period. This period was introduced in Rome Imperial
to allow the smear of an exceptional tax every 15 years.
Since Pope Gregory VII, the origin of the periods of the indication has
been set at 313: Year 1 has for indication 4. The indication does not play any
role in the calculation of the date of Easter.
v The number of
gold: rank that occupies the year in a period of 19 years, at the end of which
the phases of the moon reproduce on the same dates (cycle called the Metonic,
the name of the Greek astronomer who discovered it); Year 1 has for the number
of Gold 2. The golden number of a year is equal to the remainder of the division
by 19 of its vintage, decreased of 1. The Greeks judged this number so
important for the establishment of the calendar that they carved in gold
letters on their public monuments.
v Epact: In the
Gregorian calendar, the age of the Moon on January 1 of the Year considered,
expressed in the whole number of days from 0 to 29, 0 being the age of the new
Ø The Jewish
calendar would come up in its current form in the 4th century.
Year. The year includes 12 or 13 months
(common years or embolismic). A common year may count 353, 354 or 355 days, and
a year embolismic 383, 384 or 385 days, depending on whether it is defective,
regular or abundant. (A year called embolismic is a year that includes an
additional month of 30 days or the value of this month itself). The New Year
reproduces at the same time of the solar year, after a period of 19 years with
7 years embolismic and 12 common years. The years are counted from the
legendary date of the creation of the world, 3761 B.C.
Months. The months include 29 or 30 days.
Their names are borrowed from the Babylonian calendar: Tishri, Shevat, Nisan,
Sivan and Av count for 30 days; Tevet, Iyyar, Tammuz and Elul, 29; Cheshvan,
Kislev and Adar II (or Adar Sheni or ve-Adar) is a 29-day intercalary month,
which is added in the Embolismic years.
Festivities. Among the main festivals of the
Jewish calendar are Rosh Ha-Shanah (begun the year, towards the 1st Tishri),
Yom Kippur (10 Tishri), Hanukkah (the dedication, from 25 Kislev to 2 or 3
Teet), Passover (Easter, 14 Nisan).
Ø The Muslim
calendar is a lunar calendar.
Year. The year includes 12 lunars. The
calendar combines years of 354 days (common years) and years of 355 days
(abundant years). In relation to the Gregorian calendar, the Muslim year starts
from 10 to 12 days earlier each year. We count the years from the Hegira, the
leak of Muhammad to Medina (622).
Months. The months alternately count 30 and
29 days. The last month has 29 days in the common years and 30 days in the
Day. Muslims count the day from sunset.
Sunday is the first day of the week.
and remarkable dates.
New Year’s Day is the first day of the first month (Muharram). The hegira of
the Prophet to Medina is celebrated on the first day of the third month (Rabi
The ninth month
(Ramadan) is marked by a young absolute enter the sunrise and the sunset.
On Friday, the day of the
prayer is unemployed in many Muslim countries.
Ø The Chinese
it is a lunisolar calendar. It comprises 12 common years of 12 lunar months of
29 or 30 days ( 354 or
355 days) and 7 embolismic years of 13 months ( 383 or 384 days) on a 19-year
month. The year is
divided into 24 sections of the season or taken, each consisting of two parts, Jie
and Qi, whose beginning coincides with 24 positions special equidistant of the
sun on the ecliptic, 15 in 15 °. Their dates are mobile. A month can count up
to three sections.
Days. The counting of days is carried out
by means of a sexagesimal system: each date is spotted simultaneously in a
cycle of 10 days (celestial trunks) and in a cycle of 12 days (terrestrial
branches). 60 is the smallest common multiple of 12 and 10, after 60 days the
dates reproduce according to the same succession. Since the Han, this system is
also used for counting years.
The 12 years
of the duodenal cycle are designated by animal names.
Gregorian and Republican calendars.
Ø The Gregorian
calendar is not exactly right. The tropical year, the mean value of the
interval separating two spring equinoxes is shorter than the Julian year of 11
minutes and 14 seconds. As a result, the beginning of the Julian year slows
down gradually over that of the tropical year, from 3 days in about 400 years.
was moved by this situation because of the prescriptions of the Council of
Nicaea (325) concerning the date of Easter. While this feast was to be
associated with the first moon of spring, the gradual drift of the Julian
calendar in relation to the Equinox risked in the long run celebrating Easter
in the heart of summer.
ordered in 1582 by Pope Gregory XIII was therefore mainly aimed at restoring
the concordance between the calendar and the seasons. The Gregorian calendar
came from it.
Council of Nicaea, the spring equinox had advanced by 10 days compared to the
date of March 21. Gregory XIII ordered the deletion of 10 days between Thursday,
Oct 4, 1582, and Friday, Oct 15. The year 1582 only counts 355 days and, as of
the following year, March 21 coincides again with the spring equinox. In order
to maintain this coincidence, Gregory XIII decided, moreover, that the secular
years would cease to leap, except those which are divisible by 400
(1600.2000…). This measure allowed removing 3 days to 4 centuries.
Gregorian year is still too long for 0.003 days. In the year 4317, it will
count 1 day too many, given the cumulative error since 1582. Finally, the
beginning of the year is set for the first of January.
into force of the Gregorian calendar. In Rome, Spain, and Portugal, the Gregorian
calendar was applied on Oct 4, 1582. In France, the reform entered into force
on the night of December 9 and 10. In the Spanish Netherlands, the day after
December 14 was Christmas Day, but the Protestant provinces refused to abide by
the decree. The Catholic States of Germany and Switzerland adopted the reform
in 1584, Poland in 1586, Hungary in 1587.
Protestant countries, the resistance was long. If Prussia adopted the new
timetable dice 1610, it was only around 1700 that the Protestant provinces of
the Netherlands, Germany, and Switzerland rallied there. In Britain and Sweden,
the reform only leaked in 1752.
adopted the Gregorian calendar in 173 and China in 1911. The Orthodox countries
have kept the Julian calendar until the twentieth century: The new calendar was
adopted in 1918 in the USSR, in 1919 in Romania and Yugoslavia, in 1923 in
Greece. Its use is now universal for civic activities.
Ø The Republican
Republican calendar, set up by an act of the Convention of Oct 6, 1793, wanted
to mark a break with the Christian tradition. The years were counted (in Roman
numerals) from Sept 22, 1792, date of proclamation of the Republic, which
coincided with the autumnal equinox. In France, the Republican calendar was
legally used until January 1, 1806, but it never succeeded in imposing itself
on the population. It was abolished by Napoleon I, by a decree of September 9,
1805, which put into effect the Gregorian calendar.
Republican year has 12 months of 30 days. It ends with 5 (ordinary year) or 6
(leap year) complementary days, or without-culottes, added after the last
month. The names of the month, invented by the conventional Fabre of Eglantine,
evoke the climatic or agricultural dominance of the period to which they are
remembering and present a different ending according to the season.
is divided into 3 periods of 10 days (decades), named respectively, according
to their rank and by a Latin etymology: Primidi, Duodi, Tridi, Four-day,
Quintidi, Sextidi, Septidi, Octidi, Nonidi, Decadi.
Illustration for the month of Frimaire. Engraving by
Salvadore Tresca from a drawing by James Laffite. Discreet fur stole, frost
and hint to the hunt symbolize the last month of autumn.
(Carnavalt Museum, Paris)
Concordance between the Republican and Gregorian
The leap years of the Republican calendar, there were 6 days
holidays sans-culottides, have an asterisk.