How to find out when the patent of a compound expires?

The longest term of a patent is legal. In the absence of obstacles such as unpaid annual fees, the patent for invention is 20 years from the date of application, and the patent for utility model and design is 10 year from the date of application. A composite patent should be an invention patent, and 20 can be added directly from the date of filing (for example, the filing date is1March 992 15, and the expiration date is 201March 2 15).