The Time of Isha

1. When the redness in the western horizon after sunset goes away then the time of Isha starts.
2. The time of Isha lasts till Subh Saadiq (True Dawn – See Article: The Time of Fajr)
3. After half the night passes then it is the Makrooh time of Isha.
4. Half the night means the duration from sunset till Subh Saadiq divided by half.
5. For example, if Sunset is 6:30pm and Subh Saadiq 4am, the total number of hours of the night is 9 hours and 30 minutes. Half of this is 4 hours 30 minutes. Thus, half the night ends at 11pm. Therefore, it is Makrooh to perform Isha after 11pm.
6. Performing Isha after half the night is over reduces the thawaab of the Namaaz considerably.
7. Therefore, one should not delay the Isha to that extent.
8. It is best to perform Isha before a third of the night passes.

(Behshti Zewar)