Fasting On The Day Of Aashurah
Jazaka Allahu khaira, Br. Umer
As per my understanding, there are plenty of ahadith that talk about only fast of 10th Muharram (Ashura) and in a few Prophet (sws) did show intention to fast on 9th as well in the coming year but He (sws) passed away before that. Therefore, you can do either.