On dates and
calendars
Monthly Strategy Report December 2016
Rose Marie Boudeguer
Director, Research Services
Monthly Strategy Report. December 2016
On dates and calendars
The month of December is full of significant dates that have been a constant
in our lives; we could not conceive of them being removed from the calendar
or reconfigured entirely. Throughout history, however, there have been days that
never existed and even today there are people who live in another time, another
year, another era.
A bit of history
In 46 B.C., the emperor Julius Caesar established a calendar based on the tropical (solar) year, which, at
the time, was calculated as 365 days and 6 hours. The Julian calendar divided time into 12 months and
365 days and, to adjust for the annual 6-hour discrepancy, a leap year was established that would take
place every fourth year by adding a day to the month of February.
Subsequent studies revealed that the tropical year actually had 365 days, 5 hours, 48 minutes and
46 seconds, meaning the Julian Calendar had an 11-minute time-lag with respect to the actual cycle,
resulting in a gap of one day every 128 years.
In 325, the emperor Constantine convened the first council of Christendom, the Council of Nicaea, which
aimed to cement the unity of the Christian church following continual disputes between various factions.
The Council established the astral moment in which Easter was to be observed: the Sunday after the
full moon that follows the spring equinox. In 325, the equinox fell on 21 March, but with the passage
of time it moved up on the calendar. If this were to continue, Holy Week would be celebrated earlier
and earlier and, after several years, it would occur in another season altogether. This was unacceptable
since, according to the Bible, Jesus died and was resurrected in the Hebrew month of Nisan, meaning
springtime, and therefore, Easter must always fall in that time of year.
By 1582, the year Pope Gregory XIII decided to take action on the matter, the equinox had advanced
10 days, occurring on 11 March. How could one preserve the regularity of the liturgical calendar
without neglecting the laws of nature? Pope Gregory assembled eminent scientists who suggested the
introduction of certain corrections in the civil calendar in order to adapt it to liturgy without neglecting
the solar calendar.
And thus emerged the Gregorian calendar, which is used by much of the world today. The calendar
accounts for the difference only by changing the leap year rule. One day would continue to be added to
February every four years – the years divisible by four – excluding years that are multiples of 100, unless
the year is divisible by 400, in which case it would be a leap year.
A leap into the future
But Pope Gregory still had a problem: what to do with the 10 extra days from the Julian calendar? He
rectified it with the stroke of a pen and the days between the 4th and the 15th of October 1582 officially
ceased to exist. This leap into the future led to paradoxes, such as the funeral of Saint Teresa of Jesus,
who died on 4 October 1582 at the Alba de Tormes convent and was buried the next day, 15 October.
The Gregorian calendar was adopted gradually; centuries passed before it was implemented on a global
scale. It was first adopted by the Catholic counties – Italy, Spain, Portugal – and later by the Protestant,
Anglican, and Orthodox populations. Some countries implemented it by region; some sanctioned it all
at once, while others took years and even centuries to adopt it. Each country that implemented the
Gregorian calendar experienced a rare phenomenon: a leap into the future. In some Catholic provinces
in Flanders and southern Holland, there were no Christmas or New Years festivities as the date jumped
Monthly Strategy Report. December 2016
from Friday, 21 December 1582 to Saturday, 1 January 1583.
Great Britain and the American colonies did not implement the Gregorian calendar until 1752. Thus,
although the deaths of Shakespeare and Cervantes are commemorated on the same day, Cervantes
predeceased Shakespeare by ten days in real time. Russia only introduced it after the October Revolution,
which took place in November, according to the rest of Europe.
The Gregorian calendar still lacks precision. It generates an annual time-lag between the civil and the
tropical year of 26 seconds which, although an improvement on the Julian calendar’s 11 minutes, still
produces an error of one day every 3,300 years. But correcting this discrepancy is complicated because
it has been proven that, over time, the Earth’s rotation slows, making the days slightly longer, while the
years remain the same length. This creates a new factor that scientists are still studying, but with nearly
1,700 years until the next adjustment, they are in no hurry.
The origin of the Christian era
The Julian calendar began with the year in which the city of Rome was founded: the first year of the
Roman era, or “ab urbe cóndita” (a.u.c.). In 1284 of the Roman era, the Christian church proposed using
the birthday of Jesus as the starting point for chronological computation. The early Christians did not
celebrate the birth of Jesus – in fact only the high nobility and emperors celebrated their birthdays at
the time – so the exact date was not recorded. However, the Bible places the Annunciation of the Virgin
on 25 March in the year 753 of the Roman era. That date was taken as the day of Incarnation and the
Christians roughly calculated nine months to arrive at 25 December, although it has been suggested
that the 25th was chosen because of its proximity to the winter solstice, when pagans celebrated the
festival of Sol Invictus. So, it is possible that the selection of the date was a kind of marketing tool to
make Christianity more meaningful to pagans in an effort to convert them.
This is how the Church decided that the year 753 a.u.c. would become 1 a.i.D. (ab incarnatione Domini).
The year this decision was made (1284 a.u.c.) became 532 a.i.D. or 532 A.D. (anno Domini). There is still
tremendous controversy about the date and year of Christ’s birth, but that’s a topic for another time.
What is important is that this marked the advent of the Christian era. Nevertheless, it is curious that the
birth of Christ and the New Year are celebrated on different days, particularly after the effort involved
in pinpointing Christ’s birth to coincide with the beginning of a new era.
Other calendars
The Gregorian calendar coexists with other ancient calendars, such as the Chinese calendar, created in
2637 B.C., which consists of five 12-year cycles and in which each year is governed by a different animal.
Chinese New Year is celebrated between 21 January and 21 February on the Gregorian calendar; in 2017, it
will fall on 28 January. The Hindu and Hebrew calendars resemble the Chinese calendar in that they are
governed by solar and lunar principles and add an extra month every three years. The Islamic calendar is
based on lunar phases: each month begins the day after the new moon and the duration of each month
is never the same, nor is it repeated from one year to the next.
So, on 31 December, as we prepare to ring in the New Year, in China it will be the third day of the twelfth
month in the year 4714, the year of the monkey. For Hindus, it will be the tenth day of Pausa 1938. In
Orthodox regions that still use the Julian calendar, it will be 18 December 2016. It will be the second of
Tevet 5777 for Jews and the second of Rabi’ Al-Akhar 1438 for Muslims.
Wherever you are in the world and on whichever day, month, and year you find yourself, the Market
Strategies team from Banca March would like to wish you happy holidays.