The Gaon’s Impact on the Interpretation of both Primary Sugyot in Zemanim
…Ḥabad siddur, specifies 4 minutes. He reverses the position he took in Shulḥan Arukh HaRav, which supported Rabbeinu Tam. [29]See Zemanim Ke’hilkhatam by R. Boorstyn, chapter 2, section 3, where…

