On a calendar published in Pakistan

Question

A study concerning the times of Fajr and Isha has been published in Pakistan [stating] that the time of true dawn printed in the calendars is not correct: in blessed Ramadan, if the Fajr prayer is performed according to that time immediately after the end of the time of suhur, it falls before the true dawn. What we wish to know is: in your view, is this study correct or not? If someone performs the Fajr prayer immediately after the end of the time of suhur, will that prayer be valid or not?

Answer

I have no expertise in astronomy. Once the madrasa entrusted me with compiling a calendar for iftar and suhur. So, to research and verify [the times of] true dawn, sunrise, zawal, the two shadow-lengths, sunset and the disappearance of the twilight (shafaq)

Source: Fatawa Mahmudiyya

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