Hadith: The Prophet (may Allah's peace and blessings be upon him) used to offer the Zhuhr prayer at the time of intense heat, and the ‘Asr prayer at the time when the sun was clear, and the Maghrib prayer when its time was due
عن جابر بن عبد الله الأنصاري رضي الله عنهما قال: «كَانَ صلى الله عليه وسلم يُصَلِّي الظُّهْرَ بِالهَاجِرَة، والعَصرَ والشَّمسُ نَقِيَّة، والمَغرِب إِذَا وَجَبَت، والعِشَاء أَحيَانًا وأَحيَانًا: إِذَا رَآهُم اجتَمَعُوا عَجَّل، وَإِذَا رَآهُم أَبْطَئُوا أًخَّر، والصُّبحُ كان النبي صلى الله عليه وسلم يُصَلِّيهَا بِغَلَس». [صحيح] - [متفق عليه] المزيــد ...
Jābir ibn ‘Abdullāh al-Ansāri (may Allah be pleased with him) reported: The Prophet (may Allah's peace and blessings be upon him) used to offer the Zhuhr prayer at the time of intense heat, and the ‘Asr prayer at the time when the sun was clear, and the Maghrib prayer when its time was due, and as for the ‘Ishā' prayer, he would sometimes hasten to offer it when he saw them already gathered, and at other times he would delay it when they had not gathered yet. As for the Fajr prayer, the Prophet (may Allah's peace and blessings be upon him) used to offer it at the time when darkness at the end of the night mixed with the faint light of the morning. Sahih/Authentic. - [Al-Bukhari and Muslim]
This Hadīth clarifies the best time to offer the five daily prayers.
The Zhuhr prayer: when the sun passes its zenith; this is the beginning of its time. However, if it is too hot in a way that affects the people praying, then it is better to delay the prayer until the temperature is not as severely hot, as proven by other evidence.
The ‘Asr prayer: when the sun is still white and clear, when the shadow of everything is equal to it, after the shadow of the zenith.
The Maghrib prayer: when the sun sets.
The ‘Ishā' prayer: It depends on people. If they attend the congregational prayer at the beginning of its time, when the afterglow disappears, then they should pray. If they do not show up, then they should delay it to the time close to the first half of the night, which is the best time to offer it, as long as there is no hardship involved.
As for the Fajr prayer: its time is when light starts to mix with darkness.