Nasir al-Din al-Tusi, Shia philosopher, mathematician and theologian and author of Tajrid al-I‘tiqad, died on the day of Ghadir 672 AH in Baghdad and was buried in Kazimayn.
Uthman, the third caliph, was killed in Medina in 35 AH after rebels from Egypt, Kufa and Basra besieged his house. The people then pledged allegiance to Imam Ali.
Other views
It coincides with Eid al-Ghadir, so it is listed as a historical event (not red) to keep Ghadir’s colour. 12 Dhu al-Hijjah is also reported.