Tafsir Ibn Kathir -> Surah Al-A'raf -> The Universe was created in Six Days

Allah states that He created the universe, the heavens and earth and all that is in, on and between them in six days, as He has stated in several Ayat in the Qur'an. These six days are: Sunday, Monday, Tuesday, Wednesday, Thursday and Friday. On Friday, the entire creation was assembled and on that day, Adam was created. There is a difference of opinion whether these days were the same as our standard days as suddenly comes to the mind, or each day constitutes one thousand years, as reported from Mujahid, Imam Ahmad bin Hanbal, and from Ibn `Abbas according to Ad-Dahhak's narration from him. As for Saturday, no creation took place in it since it is the seventh day of (of the week). The word `As-Sabt' means stoppage, or break. Imam Ahmad recorded Abu Hurayrah saying: `Allah's Messenger told me:

«خَلَقَ اللهُ، (عَزَّ وَجَلَّ)، التُّرْبَةَ يَوْمَ السَّبْتِ، وَخَلَقَ فِيهَا الْجِبَالَ يَوْمَ الْأَحَدِ، وَخَلَقَ الشَّجَرَ يَوْمَ الْاثْنَيْنِ، وَخَلَقَ الْمَكْرُوهَ يَوْمَ الثُّلَاثَاءِ، وَخَلَقَ النُّورَ يَوْمَ الْأَرْبِعَاءِ، وَبَثَّ فِيهَا الدَّوَابَّ يَوْمَ الْخَمِيسِ، وَخَلَقَ آدَمَ، عَلَيْهِ السَّلَامُ، بَعْدَ الْعَصْرِ مِنْ يَوْم الْجُمُعَةِ، فِي آخِرِ الْخَلْقِ، فِي آخِرِ سَاعَةٍ مِنْ سَاعَاتِ الْجُمُعَةِ، فِيمَا بَيْنَ الْعَصْرِ إِلَى اللَّيْل»

. (Allah created the dust on Saturday, and He created the mountains on Sunday, and He created the trees on Monday, and He created the unpleasant things on Tuesday and He created the light on Wednesday and He spread the creatures through out it on Thursday and He created Adam after `Asr on Friday. He was the last created during the last hour of Friday, between `Asr and the night.)