How to determine the date of patent application? What can change the date of patent application?

According to the provisions of the Patent Law, if the applicant directly submits the application documents to the acceptance office or agency of the Patent Office, and the on-site examination meets the acceptance conditions, the filing date shall be the filing date. How to determine the date of patent application and under what circumstances can you change the application documents mailed by the applicant. If the application documents meet the acceptance conditions, the mailing date shall be the application date. If the postmark date of the mail is unclear, the postmark date of the mail sent to the Patent Office shall be the application date. If the postmark date of the mail is unclear, the date of receipt by the Patent Office shall be the application date. After the application date is determined, it cannot be changed at will. The application date can only be changed in the following two cases: ① Because the postmark is unclear, the Patent Office takes the date of receipt as the application date, or the applicant thinks that the application date set by the Patent Office is wrong, and the applicant can provide a registered receipt or other evidence of mailing the application documents and ask the Patent Office to correct it. Upon verification, the Patent Office may change the filing date. (2) For an application for a patent that has been submitted, if the applicant himself or after examination by the Patent Office finds that the instructions contain illustrations, but in fact the drawings have not been submitted or omitted, the applicant may submit it on his own initiative or within a specified time limit after receiving the notice of correction from the Patent Office. Where the drawings are submitted as required, the date of the last submission of the drawings for the application shall be the date of filing. Where the date of application is changed, the Patent Office shall promptly notify the applicant.