First of all, we would like to stress that Allah Almighty is the Sole Creator of the universe including Heavens and Earth. According to the commentators of the Qur’an, both the Heavens and Earth were created in six days. But the creation in six days is not according to our calculations (i.e. 6 X 24 hours); the exact length of creation here is known to Almighty Allah alone.
Dr. Muzammil Siddiqi, former president of the Islamic Society of North America, states the following:
“The Qur’an has mentioned in several places that Allah created the Heaven and the Earth in 6 days. (Surah 7, verse 54; Surah 11, verse 7; Surah 25, verse 69; Surah 32, verse 4; Surah 50, verse 58; Surah 57, verse 4).
However, in Surah Fussilat, Allah Almighty says: “Say: “Is it that ye deny Him Who created the earth in two Days? and do ye join equals with Him? He is the Lord of (all) the Worlds.” He set on the (earth) mountains standing firm, high above it, and bestowed blessings on the earth, and measured therein all things to give them nourishment in due proportion, in four Days, in accordance with (the needs of) those who seek (sustenance). Moreover, He comprehended in His design the sky, and it had been (as) smoke: He said to it and to the earth: “Come ye together, willingly or unwillingly.” They said: “We do come (together), in willing obedience.” So He completed them as seven firmaments in two Days and He assigned to each heaven its duty and command. And We adorned the lower heaven with lights, and (provided it) with guard. Such is the Decree of (Him) the Exalted in Might, Full of Knowledge.” (Fussilat: 9-12)
This may give the impression that the Qur’an is talking about 8 days of creation: first two days are mentioned for the creation of earth, then four days for all things on earth, then two days for the heavens. But the commentators of the Qur’an point out that the four days mentioned in the middle include the first two days also. So in other words it is said that Allah created the earth in two days and then put its provisions in it, thus altogether four days and He created the heavens in two days. Thus the total number remains six without any inconsistency in the words of Allah.
It is important to remember that the words ‘yaum’ and ‘ayyam’ (day and days) are not used in the Qur’an always to mean a 24-hour period. The day could be as long as 1000 years (Al-Hajj 22:47) or 50,000 years (Al-Ma`arij 70:4) or more.
We should not say that Allah created the Heavens and the Earth in 6 X 24 Hours. Only Allah knows the length of the days of His creation. However, there is a Divine wisdom in mentioning 6 days and this, it seems to us, to indicate order and gradation in the creation. It also points to the power of Allah as well as His Mercy that He gave His creation this time. Everyday of the week we should thank Allah and at the end of the week we should express even more thanks and plan for the next week.
The Qur’an, however, has rejected the idea which is mentioned in the Bible that Allah created the Heaven and Earth in six days and on the seventh day He took rest. Allah says in the Qur’an: “We created the Heavens and Earth and that which is between them in six days and no fatigue touched us” (Qaf:38)