“Dear virtuous Shaykh, will he (the reciter) get the reward for reciting Surah Al-Kahf (if he does it) in the night of Al-Jumuah (i.e. Thursday night); will he obtain the virtue of reciting Surah Al-Kahf?”
“No. Reciting Surah Al-Kahf is (to be done) on the day of Jumuah (on Friday), it’s recitation is (meant to be) on the day of Jumuah. And the best is when it is done after sunrise. You have time from sunrise up until sunset. If you read it at any time between sunrise and sunset you will get the reward.”
Shaykh Muhammad bin Saalih al-‘Uthaymeen, may Allah have mercy upon him
Translated by Salafi-Dawah.com.
Source: Silsilah Al-Liqa’ Ash-Shahryy, Al-Liqa’ Ash-Shahryy 69.
Taken from : http://www.salafi-dawah.com/the-best-time-for-reciting-surah-al-kahf.html