Letter from the Publisher

They were divided into three ten-day periods that were
named according to their numerical order: primidi, duodi,
tridi, etc. The decision was even taken to give each day
of the year its own name borrowed from a fruit, an animal
or a tool: October 2nd was christened Potato, October
29th Black Salsify, November 5th Turkey Cock, November
30th Pickax, December 28th Manure and January 10th
Plaster Stone! Following on from this, the revolutionaries
also replaced—albeit briefly—the duodecimal system
by a decimal system that involved a day divided into
ten hours, hours divided into ten minutes and minutes
divided into ten seconds. The Republican calendar was
rescinded in 1806.
Pre-Columbian Calendars
The grand civilizations of what is now
Latin America had also developed various
calendars. The Mayas had a very complex
system combining several calendars:
one religious with a 260-day year and
the other civilian with a 365-day year,
as well as various cycles and counting
modes. The Aztecs simultaneously used
a sacred 260-day divinatory calendar, a
civil solar calendar of around 365.25 days,
and a 584-day Venus-based calendar.
Calendars in the global era
Today, in our “global village,” the Gregorian calendar has
established itself as the international benchmark, at least as
far as everything related to civilian activities, transport and
trade exchanges. But it continued to co-exist with other
sometimes very ancient systems governing religious life and
the cadence of traditional feast days. Followers of Islam use
the Muslim lunar calendar (also called the Islamic or Hegerian
calendar) in which the year is composed of 12 months of 29
or 30 days each. This Muslim year is 11 days shorter than the
Gregorian year, which explains why the dates of Ramadan fall
progressively earlier each year. It is based on direct human
observation of the new moon that signals the start of the
month, so different locations observe different starting dates.
Moreover, the Hegira (the Muslim era) begins in 622 AD.
According to the lunisolar Jewish (or Hebraic) calendar, which
uses lunar months and solar years, months begin with the
new moon and last 29 to 30 days. So as to keep pace with the
solar rhythm, a 13th month is added to the year at certain
intervals. The seven-day week begins on Sunday and the start
of the calendar is equivalent to the year 3761 BC. The Chinese
calendar is also of the lunisolar type, with seven intercalary
months added over a 19-year cycle. The months begin with
the new moon and the Chinese New Year falls between
January 21st and February 20th. Among the many other
systems used around the world, one might also mention the
Thai lunar calendar, the Saka calendar (in India, Pakistan and
Bali), the various Hindu calendars, and the “Julio-Gregorian”
Berber calendar.
center
Signed in 1557 and attributed to German watchmaker Christoph
Schissler, this instrument presents a multiplicity of ingenious
devices. It contains a map of central and western Europe and
another of the world, a dictionary of geographic names, and a
horizontal sundial with four scales for latitudes.
top and above right
An oval-shaped astronomical watch made of silver and brass.
Movement signed Marc Girard à Blois, France, beginning of the 17th
century. Mr. Girard’s watch belongs to this relatively numerous series
of oval watches, which were fashionable from the last quarter of the
16th century until 1630.
Calendars 63 •