The Judgment Day has been described as the Great Day in many verses of the Qura’n.
Verse 37 of Surah Maryam says, “Woe to the disbelievers from the meeting of a great day.”
The explanation for the term “the punishment of the Great Day” has come for the punishment in this world too. The difference can be discerned from the preceding and following verses.
This explanation has been given because of the great events that will occur that Day. The result and the great reward, justice and the great accounting, the great assembly of the creations, the longevity of this great day, the importance of fear and terror, the importance of the beginning of the Day of Judgment . In short the greatness and importance of all that will take place.