Having briefly been reviewed the historical process of changing the formulae for determining the times of Islamic prayers, two newly found formulae and a new rule for establishing the times of prayers would be discussed. These matters have been exploited from four texts, still preserved as manuscript: (1) Siyyid ¾?y? al-D?n Sh?shtar?’s ¼ad B?b dar Macrifa al-A½??rl?b, (2) B?r?n?’s ’Ist?c?b f? cIlm al-A½??rl?b, (3) Mu¬ammad Madjd al-D?n b. Zayn al-D?n Mu¬ammad Hamid?n?’s ’An?s al-?ull?b f? Macrifa al-A½?url?b, and (4) an anonymous treatise named Al-’Ist?c?b li-’l-cAmal bi-¼adr al-Waza wa-’l-Jin?¬ al-Ghur?b. In the end, the accuracy of the numeral results derived from those formulae would be presented, by making a comparison with each other as well as with the standard rules.