The term of a purchase and sale contract is generally based on the time agreed by the parties to the contract. If the parties to the contract have not agreed or the agreement is unclear, the time specified in the supplementary agreement shall prevail. If no supplementary agreement can be reached, it shall be determined in accordance with the relevant provisions of the contract or trading habits; If the time limit for performance is not clear, it can be performed at any time, but the other party should be given the necessary preparation time. Legal objectivity:

Article 49 of the Civil Code of the People's Republic of China * * * If the parties conclude a contract in the form of a contract, the contract shall be formed when all the parties have signed, sealed or fingerprinted it. Before signing, sealing or fingerprinting, one party has fulfilled its main obligations, and the contract is established when the other party accepts it. A contract shall be concluded in writing as stipulated by laws and administrative regulations or agreed by the parties. If the parties fail to do so in writing, but one party has fulfilled its main obligations and the other party accepts it, the contract is established. Article 52 of the Civil Code of the People's Republic of China * * * A contract established according to law shall come into effect upon its establishment, except as otherwise provided by law or agreed by the parties. In accordance with the provisions of laws and administrative regulations, if the contract should go through the formalities of approval, such provisions shall prevail. If the failure to go through the formalities of approval and so on affects the effectiveness of the contract, it will not affect the performance of the obligation clauses such as approval and the effectiveness of relevant clauses in the contract. If the party who should go through the formalities of applying for approval fails to perform his obligations, the other party may request him to bear the responsibility for violating the obligations.