How long is the examination period for invention patents in China?

According to the "Twelfth Five-Year Plan for album review" (20 1 1-20 15), the actual examination period of invention patents is stable at about 24 months. According to the disclosure 18 months, the whole review process will take 3.5 to 4 years at the longest, and the time will be shortened if the disclosure is required in advance.