Circumstances of Revelation
Place: Mecca, as the theme of the verses testifies; the story of Thamūd is an indirect threat to the people of Mecca. → Introduction
Time: The early days of Islam. Al-Mizan reads the change from when it revealed her (verse 3, past tense) to when it is covering her (verse 4, present tense) as a subtle reference to the state of affairs when the sūrah was revealed, with the earth covered by the darkness of vice and transgression. → Commentary on verse 4
A summary prepared from Tafsīr al-Mīzān: where and when the sūrah was revealed, and the occasions reported for its verses, with the ʿAllāmah's view of them. Each point links to the full discussion.