The Messenger of Allah ﷺ threw the pebbles at the Jamarat at the time the sun passed its zenith, or just after it passed its zenith.
حدثنا نصر بن باب حدثنا الحجاج عن الحكم عن مقسم
رمى رسول الله ﷺ الجمار عند زوال الشمس أو بعد زوال الشمس
Its isnad is sahih. What is meant is on days other than the day of sacrifice, for as for the stoning on the day of sacrifice, it takes place in the forenoon, as in the hadith of Jabir found in Muslim, "I saw the Messenger of Allah ﷺ stone the pillar in the forenoon on the day of sacrifice alone, and after that he would stone after the sun had passed its zenith."The hadith was narrated by Tirmidhi 2:104 through Ziyad bin Abdullah from Hajjaj, and he said, its hadith is hasan. Its commentator also attributed it to Ibn Majah.