The Innovation of the Unified Adhan, and the report from Shaykh Taqi al-Din al-Halali and others that the Fajr adhan is called before its time.

The Shaykh : I hear with my own ears the adhan that is broadcast from a single mosque there. Among the innovations of this country, which it is unique in having compared to other countries—and praise be to Allah, it is unique in this—because it is an innovation, is that the adhan there is called the "unified adhan." It is broadcast on the radio so that everyone, near and far, hears it at the same time in all the mosques. Knowing that in Oman—I do not know if some of you have been there—some houses are in valleys, some on the tops of mountains, and some on the peaks of mountains. These mountains vary in height and elevation. In such a town, first of all, it is impossible for the time to be the same. The time for the one on the mountain is different from the time for the one in the valley between the mountains, in any time except for rare exceptions. The point is that we hear the Fajr adhan, and then... about half an hour later we see the true dawn, and we hear the iqamah from the mosque near us at the exact time of the dawn's appearance. That is to say: the sunnah prayers they perform before Fajr certainly occurred before the time of Fajr. As for the obligatory prayer; in the mosque near me, it takes place—praise be to Allah—in the first part of the time. As for the other mosques, they have already finished. Likewise, in Syria, we hear the broadcast while we are eating suhur in Amman, and they have already prayed Fajr and started the songs they call religious songs.
This is regarding Fajr. As for the Maghrib adhan, I see the sun has set behind the mountain while I am on the mountain. When did it disappear for those in the middle of Amman, meaning in the valley? It disappeared from them a long time ago. Nevertheless, I see the sun, and I am on a high mountain, and it has set. Ten minutes later, they call the adhan for Maghrib. The timing is not... complete!
Then I learned some of what I learned from written, printed messages, and some I learned from heard news, that in Kuwait—also—they call the adhan for Fajr about a third of an hour before Fajr. In Maghrib, also.The Shaykh : Taqi al-Din al-Halali, who was a teacher at the Islamic University, has a treatise in which he states that they call the adhan for the Fajr prayer before its time—also—by this amount.
So I advise you to observe the dawn in your area; because I have tried in some countries where it was facilitated for me. Once I climbed a tall building in al-Madinah al-Munawwarah in the month of Ramadan—I think two years ago—and we were fasting. The sun set behind it, so I broke my fast. Ten minutes later, the mu'adhdhin called the adhan. And so on!
This is a digression, and although it is long, it has a benefit. My previous answer was that the time of dislike before the adhan for Dhuhr is about ten minutes or a quarter of an hour at most; but this is on the assumption that they call the adhan at the Shari'ah time, not at the astronomical time.