[tz] Calculating dates of Ramadan
ashar at linuxpakistan.org
Wed May 16 13:12:57 UTC 2012
Even within Pakistan we have different moon sightings in different areas or
even different moon sightings in one area. For example the Imams in
Peshawar are consistently different :-)
On 16 May 2012 16:57, David Patte <dpatte at relativedata.com> wrote:
> Different countries calculate a 'secular' start of Islamic month
> differently than others. I am aware for example that the astronomical rules
> used to calculate this 'secular' stat of month are different in Egypt, than
> in Saudi Arabia or Pakistan. But the Imams have the right to declare the
> religious start of month whenever they deem fit, which in the case of some
> countries could be before the their 'secular' calculation.
> On 2012-05-16 6:29, Ian Abbott wrote:
>> On 2012-05-16 10:28, Tim Thornton wrote:
>>> Regarding calculating Ramadan:
>>> The Islamic calendar is lunar, not solar, and is about 11 or 12 days
>>> than the "normal" Gregorian calendar.
>>> Months (including Ramadan) start when the first crescent of a new moon is
>>> sighted. This varies according to the atmospheric conditions and the
>>> positions of earth, sun and moon, but can be calculated to within about a
>>> day for any given location, which is good enough for tz data in the
>>> of any further specific information for a location.
>>> There is also an ongoing debate in Islam on whether the calculated date
>>> good enough, or whether they should stick with past practice of having
>>> official observers watching the sky to announce the start of the month.
>>> What cannot be done is to say that it always falls between a given pair
>>> Gregorian calendar dates, due to its shifting.
>> In practice, how much does the observed (as in astronomical) date differ
>> from the calculated date? Does it ever start _before_ the calculated date?
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