We recall to the visitor our methodology for calculating the beginning of the month for establishing the calendar for Makkah.
After the new moon is born, we first look for the earliest crescent in the evening sky of Makkah. If it is visible, then the new month starts the next day. If not, we look further and further west until the time of fajr in Makkah. If the crescent is visible anywhere to the west before fajr in Makkah, then the new month starts on the next day, exactly as if the crescent had been visible in the evening in Makkah itself. We call this concept that of the extension of the observational zone.
The methodology for calculating the beginning of the month in Makkah can be applied to any place on earth. The month will begin next day if: (1) the new moon is born (2) if the young crescent is visible in the evening sky of the place considered, or (3) if it is visible at somewhere to the west of the place before fajr there. Otherwise the month will last 30 days.
We follow this methodology in order to determine the beginning of important Islamic dates for the various countries of the world. For several strategically chosen countries on different continents we select a town towards the eastern limit of the country. We use the eastern limit because fajr in the east is earlier than fajr in the west. If visibility is acquired for the east, then it will also be acquired for the west where fajr is even later. We avoid situations where there is visibility for the west but not for the east, because in such cases, the country will be divided into two for celebrating the feast day. For most countries, such a situation will not be acceptable. However, for Aid al Fitr, Russia constitutes an exception that we will discuss later.
We now invite the reader to consult the visibility curves for the beginning of Shawwal 1434 (Shawwal 2013). Two visibility curves are pertinent: that of 6th August 2013 and that of 7th August 2013. The new moon is born on 6th August at 21 hours 50 minutes in Universal Time UTC. The blue and green zones represent the areas of the world where the crescent can be seen with the naked eye, blue under good atmospheric conditions, green representing easy visibility.
The visibility curve for 6th August shows that the totality of the world is in a non-visibility field (black zone). No observation of the crescent will be possible anywhere. Consequently, the day of 7th August will still be a day of fasting in all the countries of the world.
The visibility curve that applies is that of 7th August. On this date, blue and green zones cover a good part of the earth to the west of Africa. We thus have to examine which countries will be able to end fasting on the evening of 7th August.
We request the reader to consult the list of countries according to the date of the beginning of ramadan 2013. He will find that all the countries of North, Central and South America as well as several African countries have begun Ramadan on 9th July 2013. These countries will have finished 30 days of fasting on 7th August 2013. They will thus celebrate Aid al Fitr on 8th August 2013.
For the other countries of the world, and according to our usual methodology, we have to choose a point of visibility, and basing ourselves on the visibility at this point, check whether Fajr in the country under consideration is before or after the visibility of the crescent.
For calculating the time of Fajr with respect to the first visibility of the moon, the choice of the point of observation is important. Looking at the visibility curve for 7th August 2013, we find that the first point of visibility in the blue zone is situated at a latitude of 42° S and 12° E.
We select as our point of observation not the first point of visibility, but a point situated in the interior of the blue zone, 3° further west in longitude. Our point of observation is situated at 40° S and 9° E. Let us call this point of observation the point P. The choice in the interior of the blue zone is dictated by the following reason:
The blue zone represents naked eye visibility under perfect observational conditions. For an individual point, such as the first point of visibility, it is not certain that such conditions will be realised. But if we place ourselves within the blue zone, we take advantage of visibility not only at the selected point of observation, but also of the probability of observation in the whole of the blue zone situated to the east of our point of observation P. Indeed, to the east of P, the crescent will be visible before it is visible at the point P itself. If Fajr in a given locality is after visibility at the point P, it will be even more so if the visibility occurs earlier than at the point P.
Let us take an imaginary example in order to clarify this point. Let us say that the visibility at the point P occurs at 04H45 in universal time UTC. Let us say that Fajr in a given locality is at 04H50, also in UTC. Since Fajr is after visibility, Shawwal will start in the place under consideration. Now, as we said before, visibility to the east of the point P will occur before that at the point P. Let us say that visibility occurs at 04H40 UTC, somewhere to the east of the point P, always in the blue zone. Fajr in the place under consideration will still be before visibility. Shawwal will start in this place.
We invite the reader who desires to deepen this reasoning to consult our detailed calculation at the following technical detail page link. He will find that the blue zone towards the east of the point P covers an area of roughly 300 000 km2. This is 44 % of the surface area of France. Within such an extensive area, the probability of sighting the crescent with the naked eye within the blue zone is almost 100 %.
Whenever possible, we ask people in whom we have confidence – astronomical observatories or groups of astronomers in different countries of the world – to photograph the young crescent for us, according to our visibility predictions based on the visibility curve of the month. The photo gallery on our site bears testimony to the exactness of our predictions and the seriousness of our calculations. Month after month, we publish photographical evidence of the very young moon. We might add that all our photographs are without optical aid.
The optimal visibility of the crescent
In his paper “A Method for predicting the first sighting of the New Crescent Moon”, the British astronomer B. D. Yallop gives the following formula for determining the best time for sighting the new moon after sunset in a given place (HM Nautical Almanac Office NAO, NAO Technical Note, Updated April 1998):
Best time of visibility of the new moon = Sunset time + 4/9 * (Difference between sunset and moonset time)
Let us now examine the situation after birth of the new moon (conjunction) on 6th August 2013 at 21H50M Universal Time (UTC) at our point of observation at 40° S and 9° W:
We will choose as time of reference for observing the crescent at the point 40° S 9° E, 17H01M on 7th August 2013 in Universal Time UTC. If, in the selected cities, Fajr in UTC is after 17H01M UTC, then Shawwal will start on 8th August 2013; otherwise, it will start next day.
For a more immediate grasp, we record the comparison between Fajr times in the selected cities and the time of best visibility in the ocean in local times and not in UTC.
Once we decided upon the point and time of visibility, we chose 3 cities situated in Oceania, 4 in Asia and 9 in Africa and in Europe. We did not choose any city in North, South and Central America. All the countries here started Ramadan on 9th July 2013 and must start Shawwal on 8th August. This is also the case with the countries in Africa that started Ramadan on 9th July 2013.
The results are depicted in the following table.
We invite the reader to consult this table carefully. The content of the columns is explicit. The 5th and 6th columns compare the times of Fajr in the selected cities with the best time of visibility at the point of observation, both times being expressed in the local time of the city. If these Fajr times occur after the time of best visibility in the Atlantic Ocean, then Shawwal will start on 8th August 2013, as explained in the last two columns.
What do we find?
It is easy to see that all the countries represented in the table will start Shawwal on 8th August 2013. Since this is also the case with all the countries that started Ramadan on 9th July 2013, we can say that the whole world – with some rare exceptions which we explain in the following paragraph – will be able to celebrate Aid al Fitr together this year, namely on 8th August 2013.
The exceptions to the date of 8th August for starting the month of Shawwal are so rare that we chose not to include them in our table. It so happens that a very small part of Russia, to the east of Okhotsk, does not fall in the extension of the geographical zone of observation defined by our point of reference.
This is also the case with some islands situated close to the International Date Line, namely the Kiribati, Samoa and Toga islands.
Thus, in a small part of Russia as well as in the above islands, Shawwal will not be able to begin on 8th August 2013. However, on the evening of 8th August, the entire world is covered by a green zone of easy visibility with the naked eye. This part of the world will celebrate Aid al Fitr on 9th August 2013.
The case of Russia is, however, special. Normally, there cannot be two dates for major festival in the same country. But we cannot reason in the same manner for a small country and one as huge as Russia, especially when only a very small portion of the country is concerned. Thus we have included Russia in our list of countries that will celebrate Aid on 8th August 2013.
We used the results obtained for establishing a list of countries according to the date of Aid al Fitr, in fact for the unique date of 8th August 2013. The reader can consult this list by clicking on eid al-fitr 2013.
The concept of the extension of the zone of observation to the west of a place before fajr in the place has allowed us to publish the dates of the beginning of Shawwal 2013 for the different countries of the world. In future we intend to integrate this concept of the extension of the zone of observation in our visibility curves themselves. This will lead us to an authentic, legitimate and rigorously exact calendar for all places in the world.