How long is Tourist (L) Visa Valid for before entry?

Hi, UK Citizen. Planning to travel around china for 1 month starting 15th October 2019. I want to apply for a Visa, how far in advance can I do it without visa expiring before entering the country?

The latest date I can submit a Visa application would be 5th September 2019 as Prior to China I will be in New Zealand for 1 month.

Thanks