 <translate> The important part for answering this question is: The fourth season began airing on October 10, 2017, and is set to run for 23 episodes on The CW until May 22, 2018.
So, the final answer is October 10 , 2017. <yor> Apakan pataki fun idahun ibeere yii ni: Akoko kẹrin bẹrẹ igbohunsafefe ni Oṣu Kẹwa Ọjọ 10, Ọdun 2017, ati pe o ṣeto lati ṣiṣe fun awọn iṣẹlẹ 23 lori The CW titi di Oṣu Karun ọjọ 22, Ọdun 2018. Nítorí náà, ìdáhùn tó gbẹ̀yìn ni October 10, 2017. 