1. Time For Fajr: It begins with the dawn of the day, and is over with the rising of the sun.
(Saheeh Muslim)

2. Time For Zuhr: The time for Zuhr begins after the setting of the sun, and lasts till the time for Asr starts, in other words the time for Zuhr remains in force till the shadow of a man attains the size equal to his height, while measuring the size of the shadow, the shadow at the time of setting of the sun, is deducted.
(Saheeh Muslim)

In extreme hot weather, to make Zuhr cool that is to offer Zuhr salat when the intensity of heat has subsided.
(Saheeh Bukhari, Saheeh Muslim)

3. Time For Asr: The time for ‘Asr’ begins, as soon as the time for Zuhr is over, that is when the shadow of a man becomes equal to his height, and persists till the sun does not look pale. (Saheeh Muslim) (While measuring the size of the shadow, the size of the real shadow should be deducted from the shadow.
(Nasai, Sanad Hassan)

4. Time For Maghrib: The time begins after sun set, and persists till the disappearance of evening twilight.
(Saheeh Muslim)

5. Time For Isha: It begins after the disappearance of evening twilight. and persists till midnight.
(Saheeh Muslim)