Zman Tefillas Mincha
Now in world of yeshivos is accepted to says that it is impossible to daven Mincha after sunset even bediavad, as not accepted rely on Rabbeinu Tam. Is this correct?
There are varied minhagim with regards to davening mincha after shkiya. Chassidim rely on the opinion of Rabbenu Tam and even lchatchila daven after shkiya. The Litvish and Bnei Yeshiva are makpid to daven before shkiya. However one who misses shkiya, bdieved may daven mincha after shkiya, as per the psak of the Mishna Brura, 233:14, who allows tefillas mincha until about 15 minutes before צאת הכוכבים. The Biur Halacha recommends making a תנאי, that if it is too late to daven mincha, this tefilla should be maariv, and the tefiila he says later [with maariv] should be for תשלומים of mincha.