"When you pray Fajr, its time is until the first part of the sun appears. When you pray Zuhr, its time is until 'Asr comes. When you pray 'Asr, its time is until the sun turns yellow. When you pray Maghrib, its time is until the twilight has disappeared. When you pray 'Isha, its time is until half of the night has passed." (Using translation from Muslim 612a)   

أَنَّ النَّبِيَّ ﷺ قَالَ إِذَا صَلَّيْتُمُ الْفَجْرَ فَإِنَّهُ وَقْتٌ إِلَى أَنْ يَطْلُعَ قَرْنُ الشَّمْسِ الْأَوَّلُ ثُمَّ إِذَا صَلَّيْتُمُ الظُّهْرَ فَإِنَّهُ وَقْتٌ إِلَى أَنْ يَحْضُرَ الْعَصْرُ فَإِذَا صَلَّيْتُمُ الْعَصْرَ فَإِنَّهُ وَقْتٌ إِلَى أَنْ تَصْفَرَّ الشَّمْسُ فَإِذَا صَلَّيْتُمُ الْمَغْرِبَ فَإِنَّهُ وَقْتٌ إِلَى أَنْ يَسْقُطَ الشَّفَقُ فَإِذَا صَلَّيْتُمُ الْعِشَاءَ فَإِنَّهُ وَقْتٌ إِلَى نِصْفِ اللَّيْلِ