Calendars
are intimately tied to the human observation of the Sun and the Moon. Thus, the universality of calendars is no
surprise, appearing in almost every human society, going back to pre-Bronze age
cultures. The development of calendars spurred many related disciplines, such
as mathematics, religion, astrology and astronomy.
The
ancients’ observation of the sun, in relation to the various constellations,
gave us the solar year. They noticed that the sun returned to the same position
every three hundred and sixty-five (plus a fraction) days. Archeologists
believe many Neolithic structures around the world, such as the Pyramid of the
Sun in Mexico, Stonehenge in England and several sites in Ancient Egypt to
serve this function. “Calendar circles” are remarkable for their profusion:
they are found all over Africa, China, India and the Americas.
The
other large, observable, heavenly body is the moon. Humans noticed that the
moon also appeared at regular intervals; two weeks in a waxing phase and two
weeks in a waning one. But a problem arose. The moon took twelve cycles of
two-week periods to complete a year—that is, 354 days, while the sun took 365
days. Another problem is that the solar year is roughly 365.25 days long, and
this one-quarter day needed accounting. Finally, both the earth’s and the moon’s
orbits have been decaying imperceptibly over time, as both are slowly moving
away from each other and from the sun.
These
issues have dogged societies, affecting things like calculating days of
worship, the time to plant crops, and to today’s problems of space flight and
satellite positioning.
Early
societies arrived at various solutions to these issues. The Hindu calendar,
known as Panchanga, combined the lunar and solar calendar, adding an extra
month called the Purushottam mas every 32-33 months, based on a complex
series of calculations, to align the sun and the moon, and to account for the fractional
days in a solar year. Unsurprisingly, many Eastern countries such as Cambodia,
Thailand and Sri Lanka follow this luni-solar method. The only differences
between these various calendars is their start date. The original Hindu calendar
has a starting date of 6,676 BC, corresponding to the start of the current
cycle of time known as Kali yuga. In Buddhist countries, the calendar starts at
the birth of the Buddha, in 563 BC.
The
Persian calendar, introduced by Omar Khayyam in the eleventh century,
calculated the length of the year with astonishing precision, as
365.24219858156 days.
The
Roman empire used to have a ten-month year, but when Julius Caesar came to
power, introduced the Julian calendar, which introduced the leap year, without
reference to the moon. While it lead to a more accurate solar calendar, it completely
disassociated the moon from calendar-keeping.
The
calendar currently used, called the Gregorian calendar, is a version of the
Julian calendar, introduced in 1582, and has as its start date the birth of
Jesus Christ.
The
calendar’s original function was to determine religious observances. Indeed, the
word is derived from the Latin ‘calends’ meaning ‘to call out,’
referring to the practice of announcing that a new moon had been sighted. In
various cultures, the Islamic, Hindu and the Chinese, the sighting of the moon
has religious significance. From the sighting of the moon, in relation to the
constellations, came astrology, which posited the influence of these
constellations (or spiritual beings associated with them) on human beings and
societies. This record of the movement of the heavenly bodies led to the
science of astronomy.
The
accuracy of calendars are important, not for recording of past, but for projection
of future events. The recent use of atomic clocks, which record the passage of
time with astonishing precision, are an absolute necessity in today’s life, necessitated
by inventions such as cell-phones, satellite communication and interplanetary
travel.
This
blog started as an exploration of Daylight Savings Time, but deviated into a
far more interesting discussion. By the way, remember to put your clocks back
by an hour this November 1st!
Mohan Ashtakala is the author of 'The Yoga Zapper," a fantasy, and "Karma Nation," a literary romance. He is published by Books We Love (www.bookswelove.com)
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