Time Zone

World Time Zone  British Summer Time Rule - Coordinated Universal Time (UTC) is a high-precision atomic time standard. UTC has uniform seconds defined by International Atomic Time (TAI), with leap seconds announced at irregular intervals to compensate for the Earth's slowing rotation and other discrepancies.

Leap seconds allow UTC to closely track Universal Time (UT), a time standard based not on the uniform passage of seconds, but on the Earth's angular rotation. Time zones around the world are expressed as positive or negative offsets from UTC. Local time is UTC plus the time zone offset for that location, plus an offset (typically +1) for daylight saving time, if in effect.

UTC replaced Greenwich Mean Time on 1 January, 1972 as the basis for the main reference time scale or civil time in various regions. As the zero-point reference, UTC is also referred to by the military and civil aviation as Zulu time
Africa - Egypt Start: Last Friday in April - End: Last Thursday in September
Namibia Start: First Sunday in September - End: First Sunday in April
Tunisia  Start: Last Sunday in March - End: Last Sunday in October
Israel Start: Last Friday before April 2  - End: The Sunday between Rosh Hashana and Yom Kippur
Australia - South Australia, Victoria, Australian Capital Territory, New South Wales,
Lord Howe Island -  Start: First Sunday in October - End: First Sunday in April
Australia - Tasmania Start: First Sunday in October - End: Last Sunday in March
New Zealand, Chatham - Start: Last Sunday in September - End: First Sunday in April
Most of the United States begins Daylight Saving Time at 2:00 a.m. on the second Sunday in March and reverts to standard time on the first Sunday in November. In the U.S., each time zone switches at a different time.
North America United States, Canada (excluding Saskatchewan and parts of Quebec, B.C., and Ontario), Mexico
Bermuda, St. Johns, Bahamas, Turks and Caicos Start: First Sunday in April - End: Last Sunday in October
U.S. and Canada beginning in 2007: Start: Second Sunday in March - End: First Sunday in November

Dr Callahan talks about how Longitude was discovered- Dr Callahan's


Basics of the Gregorian calendar - The Gregorian calendar is used in most countries today. The day begins at midnight and there are 12 months in each year. The names and length of each month of the year are as follows:
(1) January 31 days
(2) February 28 {29} days  during Leap Month
(3) March 31 days
(4) April 30 days
(5) May 31 days
(6) June 30 days
(7) July 31 days
(8) August 31 days
(9) September 30 days
(10) October 31 days
(11) November 30 days
(12) December 31 days
A common year consists of 365 days while a leap year consists of 366 days, with the extra day being added to February. The length of a Gregorian year is determined by the following rule: A year is a leap year if it is divisible by 4 and is not a century year; or if it is a divisible by 400.

Hence, 1700, 1800 and 1900 for example are common years while 2000 is a leap year. This is the difference between the Gregorian calendar and its predecessor, the Julian calendar, in which all century years were leap years. The Julian calendar has a cycle of 4 years consisting of 4 x 365 + 1 = 1461 days, giving an average year of length 365.25 days. In comparison, the Gregorian calendar has a cycle of 400 years consisting of 400 x 365 + 97 = 146 097 days. The average length of a year is hence 365.2425 days.

This is a closer approximation of the tropical year, of length about 365.2422 days. Here, we are comparing with the modern definition of the tropical year. Since the Gregorian calendar is an approximation to the tropical year, the solstices and the equinoxes will stay almost constant. Each common year is a bit shorter than the tropical year, so the March equinox, for example, will move forward a quarter day in the calendar for three years in a row. The leap year will then even it out, moving the equinox back by one day in the calendar. The equinox thus performs a “four step dance”: three small steps forward and one long step back. The old Julian calendar kept the rhythm but the Gregorian calendar will “miss a beat” three times every 400 years.

Islamic Calendar

Basics of the Muslim calendar The Islamic calendar is a strictly lunar calendar. The day begins at sunset and each year consists of 12 lunar months with no leap months.  The names of the 12 Islamic months are:
(1) Muharram           (7) Rajab
(2) Safar                  (8) Sha baan
(3) Rabi-ul-Awal       (9) Ramadhan
(4) Rabi Athani        (10) Shawwal
(5) Jamada Alula       (11) Thul Qi’dah
(6) Jamada Athaniah (12) Thul Hijjah
Since the Islamic calendar is not related to the tropical year, Islamic dates move about 11 days backward each year. They do not have Leap Month. Western sources often mention an arithmetical Islamic calendar in which each year consists of 12 months and the number of days in each month alternate between 29 and 30. An extra day is intercalated in the last month according to a fixed system.

Time Zone However, this calendar is not currently used in any Muslim community. Instead, an astronomical calendar based on lunar visibility is used. In the Islamic calendar, the first sighting of the new moon marks the beginning of the lunar month. Now, a new moon is normally not visible until it is more than 24 hours old. Hence, Islamic months usually start one or two days after the Chinese months. In addition, the instant when a new moon can first be observed depends on the latitude and the longitude of the observer. Bad weather conditions also contribute to uncertainty in the sightings. As such, it is not uncommon for festive celebrations to be held on different days by communities living in different areas of a country.

Figh Council of North America Decided On Astronomical Calculations For Islamic Dates
The Fiqh Council of North America is an independent body, comprised of qualified Islamic scholars in North America. The Council communicates with experts and consultants to meet expected needs for rulings and advice in various areas of Islamic life in North America. ISNA’s Majlis Ash-Shura, the highest policy making body of ISNA, has resolved to follow the Fiqh Council’s position on the issue of determining the beginning of the Islamic lunar months for North America. According to the scientific criteria for determining the Islamic Lunar dates adopted by the Fiqh Council of North America, the last day of Ramadan will be Sunday, October 22 and Ist of Shawwal is on Monday, October 23, 2006.

Eidul Fitr 1427 - will be on Monday, October 23, 2006
The Astronomical New Mooning (Conjunction) will occur on Sunday, October 22, 2006, at 5:15 a.m. Universal Time, i.e., 1:15 am Eastern Daylight Time - or Saturday, October 21, 10:15 pm Pacific Daylight Time. At sunset in Nome, Alaska, hilal will be formed (angle is 10.8? >Danjon Limit), and its age is 22 hours. At San Diego, angle is 9.8? >Danjon Limit, and moonset is 8 minutes after sunset so it is present above the horizon. At Longitude 179:59W and latitude 45:00S Moonset is 71 min after sunset. Age is 25.4 hours and is 11.3 degrees above horizon.
On October 22, this moon will be sightable at the South West coast of South America, which is East of North America. This moon will be easily sightable (weather permitting) in Polynesian Islands on October 22.

Dr. Muzammil Siddiqi explains the decision of the Fiqh Council of North America about using astronomical calculations to affirm the month of Ramadan.

Lunar Calendar

Basics of the Chinese calendar The Chinese calendar is a lunisolar calendar with the day beginning at midnight. Lunar months form the basis of this calendar. There are 12 months in a common year. A 13th month is intercalated from time to time to keep in the calendar in line with the seasons. The Chinese divide the ecliptic into 24 equal regions of 150 each. These regions form the 24 solar terms, an important principle required to explain some of the rules of the Chinese calendar. The even terms are called major solar term, while the odd ones are called minor solar terms.

It is important to note that the given dates are only approximate as the Gregorian calendar is an approximation of the tropical year. The insertion of leap days and the fact that the Gregorian year is a little longer than the tropical year causes the dates to shift. The rules for the Chinese calendar have changed many times. In this section, we will highlight the rules for the current Chinese calendar that has been used since the last calendar reform in 1645.
Rule 1 - Calculations are based on the meridian 1200 east. Before 1929, the computations were based on the meridian in Beijing (116025'). But in 1928, China adopted the standard time zone based on 1200 east.
Basics of the Indian calendar The Indian calendar is probably the most complicated calendar in common use in the world today. There are over 30 different calendars in use in India, both solar and lunisolar calendars. For civil purposes, some states in India use a solar calendar while some states use a lunisolar calendar. But all states use a lunisolar calendar for religious purposes. There are many regional variations, but we will follow the Tamil conventions. This means that we will not discuss the full-moon to full-moon calendars that are common in northern India.

The solar calendar is based on the sidereal year. The ecliptic is divided into 12 equal regions of 300 each, which are known as rasis. This is similar to the used in the Chinese calendar. The names of the 12 rasis are:
(1) Mesha        (7) Tula
(2) Vrishabha    (8) Vrischika
(3) Mithuna      (9) Dhanus
(4) Karkata      (10) Makara
(5) Simha        (11) Kumbha
(6) Kanya        (12) Mina
The entry of the sun into each rasi marks the start of a new month and the time of entry into a rasi is called the samkranti. The time it takes for the sun to move through one rasi is called the sidereal solar month. The number of days in each solar month varies from 29 to 32. This is because the sun does not move at a constant speed along the ecliptic.

Each day begins at Sunrise. Which is called Vara the day of the week. According to Tamil conventions, the new month begins on the same day if the samkranti takes place before sunset. Otherwise, the month begins on the following day. The sidereal year begins on the first day after the mesha-samkranti.

The lunisolar calendar Like the Chinese calendar, the Hindu lunisolar calendar contains 12 lunar months in a common year and a 13th month is sometimes intercalated to keep the calendar in line with the seasons. Like the solar calendar, the day begins with sunrise. The year starts with the beginning of the month Chaitra. Each month begins on the day of a new moon. This system is called the amanta system. The alternative is to use the purnimanta system in which the month is from one full moon to the next.
The names of the 12 lunar months are:
(1) Chaitra       (7) Asvina
(2) Vaisaka      (8) Kartika
(3) Jyaishtha    (9) Margasirsha
(4) Ashadha      (10) Pausha
(5) Sravana      (11) Magha
(6) Bhadra       (12) Phalguna
The rule of intercalation of months in the Hindu calendar is similar to the Chinese system. In addition, months can be extracalated (skipped) in the Hindu calendar. The length of a solar month varies from about 29.318 to 31.644 days while the length of a lunar month varies from about 29.305 to 29.812 days. The variation can lead to two possibilities. A lunar month can be completely contained in a solar month. This means there is no samkranti in the lunar month. When this happens, this lunar month is a leap month and the following month is given the same name as the leap month.

Summer Time

From the last Sunday in March until the last Sunday in October the UK moves its clocks forward from Greenwich Mean Time by one hour (GMT+1).  This is known as British Summer Time or BST for short.  The UK is the United Kingdom of Great Britain and Northern Ireland.  Great Britain consists of England, Wales and Scotland. Since 1996 all clocks in the European Union, of which the UK is a member state, have changed on same dates and at the same time, 1am GMT. Starts: Last Sunday in March  End: Last Sunday in October. Time: 1.00 am (01:00) Greenwich Mean Time (GMT)

Explains map and globe differences, latitude, longitude, legends, scale, time zones, poles and more.
The day One remnant of change from observational lunar calendars to computed lunar calendars is in the convention for the start of the day. The first visibility of the lunar crescent will occur in the West after sunset. For a calendar that starts the month with the first visibility of the lunar crescent it makes sense to start the day at sunset. However, if the month starts with the new Moon, it may be more natural to start the calendar day with sunrise or midnight. Astronomers, however, are nocturnal, and may prefer to start the day at noon. Greenwich Mean Time (GMT) is actually measured from noon whereas Coordinated Universal Time (UTC) is measured from midnight. However, few use the noon measurement and most refer to GMT as if it were actually UTC.

Many people are confused by the acronym UTC for Coordinated Universal Time. Some believe that the acronym is based on the French name, but the story is actually even more interesting. In 1970 the Coordinated Universal Time system was devised by an international advisory group of technical experts within the International Telecommunication Union (ITU).

The ITU felt it was best to designate a single abbreviation for use in all languages in order to minimize confusion. Since unanimous agreement could not be achieved on using either the English word order, CUT, or the French word order, TUC, the acronym UTC was chosen as a compromise.When converting between calendars that start the day at different times, we will always match the main daylight parts of the days. So today means the Western or Chinese day that started at midnight, the Muslim day that started at sunset last night and the Indian day that started at sunrise this morning.

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