When is the middle of the night to which the 'Isha' prayer is delayed?

The questioner : Well, Shaykh — may Allah reward you with good — regarding the time of 'Isha', I mean the end of the time for 'Isha'... is it twelve o'clock...?

The Shaykh : No, it is something related to the difference between the seasons. That is, when the night and the day are equal, the night is twelve hours, and in this case, the middle is at six o'clock. But the night may be long and the day may be short, so one must be careful and... I mean, for example, what time does the sun set for you today? Six and a half?

Another questioner: Yes.

The Shaykh : Six and a half. The Shaykh : Well, if the sun sets at six and a half, that means the night has begun. When does the dawn end? Five and a half. That means eleven hours. So you take half of eleven, which is five and a half. If you add five and a half to six and a half, what do you get? Twelve. But this is not fixed; it either increases or decreases depending on the advancement or delay of the sunset. This is the middle of the night. It is not a fixed thing; rather, it is variable, just like the Maghrib adhan and the Fajr adhan. The text on this is explicit: that the time for 'Isha' is the middle of the night. Because the Prophet (peace and blessings be upon him) said, as in Sahih Muslim from the hadith of 'Abdullah ibn 'Amr ibn al-'As, when the Prophet (peace and blessings be upon him) mentioned the times of the prayer, he said: until the middle of the night. So you, O caller to prayer, must observe this, and you, O imam, or you, O Muslim in general; if you are afflicted with delaying the prayer, it is not permissible to delay it to more than after the middle of the night.
Other than that?