Sheikh `Abdul-Majeed Subh, a prominent Azharite scholar, states: “Almighty Allah told us that “The sun and the moon follow a reckoning.” (Ar-Rahman: 5) So, Almighty Allah made the sun and the moon a reckoning for people. This is the doing of Allah, indeed. But He made the lunar months a calendar and reckoning for Hajj and fasting. He also made the solar timing a reckoning for the times of Prayers. The time for Fajr begins with the onset of the second Fajr when the brightness that appears along the horizon in the east and extends north to south. The time of Zuhr starts when sun passes its zenith, i.e., passes the highest part of the sky, and starts to descend towards the west. The time for ‘Asr begins when the length of an object’s shadow becomes equal to the length of the object itself plus the length of its shadow at the zenith. The time for Maghrib starts when the sun sets, until the twilight or red afterglow has faded. The time for ‘Isha’ begins when the red afterglow disappears from the sky until midnight.
Thus, He made the Solar timing a reckoning for Prayer times and the lunar calendar a reckoning for Fasting and Hajj. So, Islam did not ignore the solar calendar as some may imagine. Almighty Allah made the lunar calendar a reckoning for fasting and Hajj in order for these two acts of worship to be circulated on the four seasons. Thus, a Muslim observes fasting of Ramadan in summer and he may witness Ramadan in Autumn, winter or Spring with the passage of years. So, a Muslim is trained to fast in all atmospheres. The same applies to Hajj. Given the above, it becomes clear that Islam paid attention to the lunar and solar calendars.”