Ramadan changes every year because the Islamic calendar follows the lunar cycle, which is about 10-11 days shorter than the solar year. This causes Ramadan to shift across different seasons over time. The Quran emphasizes the importance of the lunar calendar in determining Islamic dates, including fasting and Hajj. Unlike the Gregorian calendar, which lacks a fixed natural sign, the lunar calendar relies on the visible phases of the moon, making it a clear and divinely ordained system.

If doing exercise or sports will lead to you becoming weak and tired, and you won’t be able to pray Tarawih, then they are makruh because you will miss out on one of the virtuous acts in Ramadan.