The period of validity of a visa refers to the period of validity of the visa itself. The holder of a visa is eligible to enter China at any time prior to the expiry of its period of validity (allowed to enter China even before the 24:00 hour of the last date of its period of validity), so long as the entries granted on the visa have not been used up.
A visa becomes effective from the date of issuance. The visa automatically becomes invalid once its period of validity expires regardless of whether its entries are used up or not.
Chinese Embassies and Consulates-General do not extend the period of validity of an issued visa. Holder of an issued visa should apply for a new visa if he or she intends to visit China after the expiry of the issued visa. Foreigners holding an expired visa shall be refused entry into China. Make sure the visa is valid before you set off for China.