Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) used to say: "The declining of the sun" [Surah al-Isra: 78] means "when the shadow turns back", and "the darkness of the night" [Surah al-Isra: 78] means "the gathering of the night and its darkness".
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 1679