(And it is said): "This is the Day of Judgment and Distinction (between truth and falsehood, between the righteous and the sinful – the Day) that you used to deny."
“This is the time of discernment, which you denied!”
Sayyed Abbas Sadr-Ameli
(They will be told:) This is the Day of Separation (of right and wrong), which you used to belie.
Al-muntakhab fi tafsir al-Qur'an al-Karim
There and then they will be told: "This is the Day of Judgement and final decision, the Day on which the faithful are segregated from the infidels, this is the Day you have always denied