Is it allowed fast on the first day of Muharram or Suro 1st, How about the legal verdict on this?

كَرِيْمُ Allahumma ma „amiltu min ‚amalin fî hadzihi sanati ma nahaitani ‚anhu, wa lam atub minhu, wa hamalta fîhâ ‚alayya bi fadhlika ba’da qudratika ‚alâ ‚uqûbatî, wa da’autanî ilat taubati min ba’di jarâ’atî ‚alâ ma’shiyatik. Fa innî astaghfiruka, faghfirlî wa mâ ‚amiltu fîhâ mimmâ tardhâ, wa wa’attanî ‚alaihits tsawâba, fa’as’aluka […]