Complex sentence: Calhoun was also honored by his alma mater, Yale University, which named one of its undergraduate residential colleges "Calhoun College" until February 11,2017, when it was announced that the college would be renamed because of Calhoun's pro-slavery legacy.
Split into simpler sentences: Calhoun was also honored by his alma mater, Yale University, which named one of its undergraduate residential colleges "Calhoun College" until February 11,2017. On that date, Yale announced that the college would be renamed because of Calhoun's pro-slavery legacy.