وَجَعَلْنَا الَّيْلَ وَالنَّهَارَ اٰيَتَيْنِ فَمَحَوْنَآ اٰيَةَ الَّيْلِ وَجَعَلْنَآ اٰيَةَ النَّهَارِ مُبْصِرَةً لِّتَبْتَغُوْا فَضْلًا مِّنْ رَّبِّكُمْ وَلِتَعْلَمُوْا عَدَدَ السِّنِيْنَ وَالْحِسَابَۗ وَكُلَّ شَيْءٍ فَصَّلْنٰهُ تَفْصِيْلًا ( الإسراء: ١٢ )
Wa ja'alnal laila wannahaara Aayatayni famahawnaaa Aayatal laili wa ja'alnaaa Aayatan nahaari mubsiratal litabtaghoo fadlam mir Rabbikum wa lita'lamoo 'adadas sineena walhisaab; wa kulla shai'in fassalnaahu tafseelaa (al-ʾIsrāʾ 17:12)
And We have made the night and day two signs, and We erased the sign of the night and made the sign of the day visible that you may seek bounty from your Lord and may know the number of years and the account [of time]. And everything We have set out in detail. (Al-Isra  : 12)
1 Mufti Taqi Usmani
We have made the night and the day two signs, then We made the sign of night marked by darkness and the sign of day bright, so that you may seek grace from your Lord, and that you may know how to number the years and how to compute, and We have expounded everything in detail.