Complex sentence: In 2013, it was announced that Host Jon Stewart would be leaving the show to direct his first film titled "Rosewater" and that correspondent John Oliver would be replacing him as host for the summer months.
Split into simpler sentences: In 2013, it was announced that Host Jon Stewart would be leaving the show to direct his first film titled "Rosewater". It was announced that correspondent John Oliver would be replacing him for the summer months.