The claim that the annual calendar involves claiming knowledge of the unseen

His second question says: The annual calendar in which the dates and prayer times are written in advance—does the one who writes it know the times in advance, when only Allah knows the unseen? Is using the calendar forbidden? And what is the ruling on one who makes the calendar?
Answer: Calendars are known; they have known methods and a known calculation. This is not from the knowledge of the unseen. They have a known calculation for determining the entry and exit of the month, and for determining the days and nights by minutes and hours. All of this is a known matter with known mathematical methods; it is not from the knowledge of the unseen. So you should not think that it is from the knowledge of the unseen, O questioner. Rather, these are known matters with known methods and calculations, upon which the calculators proceed and they understand their meaning. So there is nothing in them from the knowledge of the unseen. Yes.