How do we respond to those who claim that the current prayer times are based on astronomers' calculations?

Question:
May Allah reward you, Honorable Shaykh. This is a question that has been asked repeatedly. It asks: What is the response to those who say, "You pray according to the calendar, which is the work of astronomers, and you fast according to it as well"?

Answer:
We pray according to the calendar. We pray at the setting of the sun. We pray at the disappearance of the twilight. We pray at the appearance of the dawn. We pray when the sun is at its zenith in the middle of the sky. These signs are clear. We pray according to them, and praise be to Allah. We do not pray according to the calendar alone. If the calendar contradicted these things, we would not act upon it. Yes.