When does the time for the 'Isha prayer end?

The 'Isha prayer must be performed before midnight, based on the Prophet's saying: "The time for 'Isha is until midnight." Midnight is calculated based on astronomical cycles. So, if the night is ten hours long, it is not permissible to delay it past the end of the fifth hour. It is preferable to perform it during the first third of the night, and it is recommended to delay it for some time, but there is no harm in performing it at the beginning of its time after the twilight disappears.