Allah SWT says: وَجَعَلْنَا الَّيْلَ وَالنَّهَارَ ءَايَتَيْنِ ۖ فَمَحَوْنَآ ءَايَةَ الَّيْلِ وَجَعَلْنَآ ءَايَةَ النَّهَارِ مُبْصِرَةً لِّتَبْتَغُوا فَضْلًا مِّنْ رَّبِّكُمْ وَلِتَعْلَمُوا عَدَدَ السِّنِينَ وَالْحِسَابَ ۚ وَكُلَّ شَىْءٍ فَصَّلْنٰهُ تَفْصِيلًا "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." (QS. Al-Israa 17: Verse 12) * Via the Beautiful Qur'an http://quran-en.com