This universal and continuous calling of the Adhan shall not cease until the Day of the Judgment
Let us begin with Indonesia right on the eastern side of the earth's central land mass. Indonesia consists of numerous small islands, the principle ones amongst them being Java, Sumatra, Borneo and Saibil, all of which are well known. It is the largest country in the world, with 180 million inhabitants. The number of non-Muslims here is negligible.
As soon as dawn breaks on the eastern side of Saibil, at approximately 5:30 am local time, Fajar Adhan begins. Thousands of Muazzins in eastern Indonesia commence proclaiming the Tawheed (oneness) of the Almighty, Omnipotent and Omniscient Allah(SWT) and Risaalat (Universal Apostleship) of the Prophet Muhammad (PBUH).
The process then continues and advances towards the Western Islands of Indonesia. The time difference between the eastern and western islands of Indonesia is one and a half hours. So one and a half hours after the Adhan has been completed in Saibil, it echoes in Jakarta on Java Island. Sumatra then follows suit.
Before this auspicious process of calling Adhan ends in Indonesia, it has already begun in Malaysia. Burma is next in line, and within an hour of its commencement in Jakarta, it reaches Dacca, the capital city of Bangladesh. No sooner the calling of Adhan ends in Bangladesh, it has already prevailed in western India, from Calcutta to Srinagar. It then advances towards Bombay and the environment of entire India resounds with this august proclamation.
Srinagar and Sialkot (a city in north Pakistan) have the same timing for Adhan. The time difference between Sialkot, Kota, Karachi and Gowadar (a city in Baluchistan, a province of Pakistan) is forty minutes, and within this time, Fajar Adhan is heard throughout Pakistan. Before it ends there, however, it has already begun in Afghanistan and Muscat.
The time difference between Muscat and Baghdad is one hour. Adhan resounds during this one hour in the environments of Hijaaz-e-Muqaddas (Holy cities of Makkah and Madinah), Yemen, United Arab Emirates, Kuwait and Iraq.
The time difference between Baghdad and Alexandria in Egypt is again one hour. Adhan continues to resound in Syria, Egypt, Somalia and Sudan during this hour. Alexandria and Istanbul are situated on the same geographical longitude. The time difference between eastern and western Turkey is one and a half hours, and during this time it is echoed with the call to prayer.
Alexandria and Tripoli (capital of Libya) are located at an hour difference from one another. The process of calling Adhan thus continues throughout the whole of Africa. Therefore, the proclamation of the Oneness of Allah (SWT) and the Prophethood of Muhammad (PBUH) that had begun in the eastern islands of Indonesia reaches the Eastern Shore of the Atlantic Ocean after nine and a half hours.
Prior to the Adhan reaching the shores of the Atlantic, the process of Zohar Adhan has already commenced in eastern Indonesia, and before it reaches Dacca, Asar Adhan has started. This has hardly reached Jakarta one and half hours later. Then the time of Maghrib becomes due, and no sooner has Maghrib time reached Sumatra, then the time for calling Isha Adhan has commenced in Saibil. When the Muezzins of Indonesia are calling out Fajar Adhan, the Muezzins in Africa are calling out the Adhan for Isha.
There is not a single moment when few thousands if not hundreds of thousands of Muezzins around the world are not proclaiming the Oneness of Almighty Allah (SWT) and the Apostleship of the noble Prophet(PBUH) on the surface of this earth. Insha Allah this universal and continuous calling of the Adhan shall not cease until the Day of the Judgment.