Job curses the day of his birth, saying, "Let the day perish on which I was born" (Job 3:3). This begins his first extended speech after the seven days of silence (Job 3:1–3).
In Job 3:3–7 Job does not curse God or other people; he curses the time of his own beginning. He speaks as if the day of his birth and the night of his conception could be erased from the calendar. He calls for that day to be swallowed by darkness and for that night to lose its place among the months. These lines begin Job’s first long speech after the narrative opening where he loses his children, wealth, and health, and then sits in silence with his friends for seven days (Job 1–2; Job 2:13). Chapter 3 shifts into poetry and gives voice to raw grief.
Job’s first speech begins by aiming his anguish at time itself: the day he was born and the night his conception was announced (explicit in verses 3–4). He speaks as if those dates could be erased—made dark, uncounted, and stripped of any festive meaning (explicit in verses 4–7).
A careful answer keeps the immediate passage, the book's argument, and the whole-Bible storyline together, so the question is answered in context instead of as a detached idea.
Start with Job 3:3, then read the surrounding section so the answer stays connected to the passage's flow.
3"Let the day perish in which I was born, The night which said, `There is a man-child conceived.`