Complex sentence: The new capital of Eastern Jin was created at Jiankang, where modern day Nanjing is today, it was during this time that the Nanjing dialect started to transform into Jianghuai Mandarin from Wu.
Split into simpler sentences: The new capital of Eastern Jin was created at Jiankang, where modern day Nanjing is today. It was during this time that the Nanjing dialect started to transform into Jianghuai Mandarin from Wu.