What day of the week was it when Imam Hussein (AS) was martyred?

Hazrat Aba Abdillah Al-Hussein (PBUH) was martyred in the afternoon of Friday the 10th of Muharram (Ashura) in the year 61 AH in the land of Karbala by Shamar Ibn Dhi Al-Jushn (1) and with his martyrdom he insured Islam forever.

1. Sheikh Abbas Qommi, Muntahal Aamal,Vol. 1, pp. 629 and 726