The word(s) "when" appears 916 time(s) in 828 verse(s) in Quran in Mohsin Khan translation.

(411) [Musa (Moses)] said: "Your appointed meeting is the day of the festival, and let the people assemble when the sun has risen (forenoon)."

(412) [Musa (Moses)] said: "O Harun (Aaron)! What prevented you when you saw them going astray;

(413) The Day when the Trumpet will be blown (the second blowing): that Day, We shall gather the Mujrimun (criminals, polytheists, sinners, disbelievers in the Oneness of Allah) blue or blind-eyed with thirst.

(414) We know very well what they will say, when the best among them in knowledge and wisdom will say: "You stayed no longer than a day!"

(415) And (remember) when We said to the angels: "Prostrate yourselves to Adam." They prostrated themselves (all) except Iblis (Satan) he refused.

(416) Then, when they perceived (saw) Our Torment (coming), behold, they (tried to) flee from it.

(417) And when those who disbelieved (in the Oneness of Allah) see you (O Muhammad صلى الله عليه وسلم), they take you not except for mockery (saying): "Is this the one who talks (badly) about your gods?" While they disbelieve at the mention of the Most Gracious (Allah). [Tafsir Al-Qurtubi].

(418) And they say: "when will this promise (come to pass), if you are truthful."

(419) If only those who disbelieved knew (the time) when they will not be able to ward off the Fire from their faces, nor from their backs, and they will not be helped.

(420) Say (O Muhammad صلى الله عليه وسلم): "I warn you only by the revelation (from Allah and not by the opinion of the religious scholars and others). But the deaf (who follow the religious scholars and others blindly) will not hear the call, (even) when they are warned [i.e. one should follow only the Qur'an and the Sunnah (legal ways, orders, acts of worship, and the statements of Prophet Muhammad صلى الله عليه وسلم, as the companions of the Prophet صلى الله عليه وسلم did)] .