Is the adhan called according to the calendar, or is it obligatory to observe the time for every prayer?

Question:
May Allah reward you. The questioner asks: Does the mu'adhdhin call the adhan according to the calendar, given that these calendars do not determine the time of prayer? What is required of the mu'adhdhin? Does he have to observe the time for every prayer? And may Allah reward you with good?

Answer:
If the time is observed, that is good. That is the default. The default is that he observes the time: he sees the setting of the sun, he sees the appearance of the dawn, he observes the shadow during the day. That is the default. But if he is not skilled in these things, or if he is blind and cannot see the appearance of the dawn, or if he is blind, then he asks the people of expertise. He asks the people of expertise, and there is no harm in him relying on the calendar. The calendar is not the same as the calendar that the state has promulgated and adopted. He relies on the one adopted by the rulers. He relies on the one adopted by the authorities. As for the calendars that have not been adopted by the authorities, he verifies them. If they are correct, he relies on them. If they are not correct, he leaves them. Yes. Therefore, the one adopted by the authorities must be repeated, must be observed, and must be scrutinized.