This document discusses calendars and how they relate to culture and society. It provides definitions of culture and calendars, and explains how different cultures track time using solar calendars, lunar calendars, and lunisolar calendars. Singapore recognizes holidays from various religious traditions through its calendar, which is reflected in its multicultural society. Movable festivals like Chinese New Year shift from year to year depending on lunar cycles and seasons. Calendars aim to synchronize astronomical cycles but require intercalation to harmonize mismatches between whole numbers and irrational periods of time.

1. Astronomy, Calendar & Society
Galaxy Forum 2013
Southeast Asia
21st Century Galaxy Education

2. Astronomy, Calendar & Society
Singapore is a multicultural society.
This is reflected in the official annual
public holidays in Singapore.

3. Culture defined
 Culture is a term used by social scientists for a
people's whole way of life. It includes arts, beliefs,
customs, inventions, language, technology and
traditions.
Anthropologist James Spradley gave an elegantly succinct
definition of culture, in which every word was carefully
chosen:
“Culture is the acquired knowledge people use
to interpret experience and generate behaviour.”

4. The English word calendar is derived from the Latin
word kalendae, which was the Latin name of the first
day of every month.
A calendar is a bunch of papers stapled together
for people to keep track of the days or holidays.
– Kristen Mathieu
A calendar is a system of organizing days for social,
religious, commercial, or administrative purposes.
This is done by giving names to periods of time,
typically days, weeks, months, and years. A date is the
designation of a single, specific day within such a
system.

5. *
* The Holidays Act was passed by the
Singapore Parliament in December 1966.

6. The Majlis Ugama Islam Singapura (MUIS), also known as
the Islamic Religious Council of Singapore, is to advise the
President of Singapore on all matters relating to Islam in
Singapore. “The Islamic Calendar for Singapore” is
published annually.

10. In Singapore, the Hindu Endowments Board makes an
estimate of the date of Deepavali for the year, and waits for
calendars from India to appear before the date of the public
holiday is confirmed by the Ministry of Manpower.

12. The Purple Mountain Observatory in Nanjing is the statutory
organization to compile the traditional calendar of China
based on astronomical calculations and historical rules on
intercalation. “The Chinese Calendar of 200 Hundred Years
(1901 – 2100)” was published in 1994.

14. Dates of Movable Festivals
Festival 2013 2012 2011
Chinese
10 Feb 23 Jan 3 Feb 21 Jan ↔ 21 Feb
New Year
Good
29 Mar 6 Apr 22 Apr 20 Mar ↔ 23 Apr
Friday
Vesak
24 May 5 May 17 May 6 May ↔ 5 Jun
Day
Hari Raya About 11 days
8 Aug 19 Aug 30 Aug
Puasa earlier each year
Hari Raya About 11 days
15 Oct 26 Oct 6 Nov
Haji earlier each year
Deepavali 3 Nov 13 Nov 26 Oct 13 Oct ↔ 14 Nov

18. Equinox

19. People watched the sun rise during a winter solstice celebration
at Stonehenge in Wiltshire, England.

21. This 2300-year-old solar observatory was discovered at Chankillo in
coastal Peru. In comparison, the earliest portion of Stonehenge is
said to have been completed around 3000 BCE.

22. Tide Chart: high tides and low tides in Singapore March 9, 2013

23. In astronomy, several kinds of year are distinguished,
having slightly different lengths. The solar year, also
called tropical year, or year of the seasons, is the
interval between two successive passages of the Sun
through the vernal equinox. Note that any start and
end point could be used as long as the Sun reappears
in the same position one year later.
One mean solar year is
approximately 365.24218967 days long
(365 days, 5 hours, 48 minutes and 45.1875 seconds)

24. A solar calendar is based on perceived seasonal changes
synchronized to the apparent motion of the Sun; an
example is the Gregorian calendar.
A lunar calendar is synchronized to the motion of the
Moon (lunar phases); an example is the Islamic calendar.
A lunisolar calendar is based on a combination of both
solar and lunar reckonings; examples are the traditional
calendar of China, the Hindu Calendar in India or
the Hebrew calendar.

25. The fundamental problem of the calendar
is the imperfect divisibility of whole
numbers into an irrational number
(fitting whole days into a month; fitting whole
days or whole months into a year).

26. A typical solution for forcing synchronization
is called 'intercalation'.
This is an artificial harmonization that, after
the fractional remainders have sufficiently
accumulated, adds a whole day (or month)
into the cycle.
An alternative solution is to ignore the
mismatch and simply let the cycles continue
to drift apart.

27. The general strategies include:
The solar calendar solution, which fits artificial
months into the year, adding an extra day into one
month when needed, while ignoring the lunar cycle
of new/full moons.
The lunar calendar solution, which fits days into the
lunar cycle month, adding an extra day when
needed, while ignoring the annual solar cycle of the
seasons.
The lunisolar calendar solution, which keeps both
the lunar and solar cycles, adding an extra month
into the year when needed.

28. Dates of Movable Festivals
Festival 2013 2012 2011
Chinese
10 Feb 23 Jan 3 Feb 21 Jan ↔ 21 Feb
New Year
Good
29 Mar 6 Apr 22 Apr 20 Mar ↔ 23 Apr
Friday
Vesak
24 May 5 May 17 May 6 May ↔ 5 Jun
Day
Hari Raya About 11 days
8 Aug 19 Aug 30 Aug
Puasa earlier each year
Hari Raya About 11 days
15 Oct 26 Oct 6 Nov
Haji earlier each year
Deepavali 3 Nov 13 Nov 26 Oct 13 Oct ↔ 14 Nov

29. Vesak Day
5th Full Moon
Good Friday
Chinese New Year After 3rd Deepavali
2nd New Moon Full Moon 11th New Moon
Winter Spring Summer Autumn Winter
Solstice Equinox Solstice Equinox Solstice
(around 21 (around 20 (around 21 (around 22 (around 21
December) March) June) September) December)

30. Thanks for listening