Trip to New Zealand via China

Hi,

My travel is from Delhi(India) to Christchurch(New Zealand) via Guangzhou(China). On return as well, the lay over is in Guangzhou(China).
There is a lay over of 18 hrs in Guangzhou while travelling from India to New Zealand and a layover of 2 hrs in Guangzhou while returning.

Could you please help me to know if visa is required or not in GuangZhou (China)? And is there any terminal change at the Guangzhou airport?