In thuleen solution, a license certificate is a certificate with a pair of start and end date/time. Every time a new license is issued or renew, the dates will be incorporated in the newly minted certificate.
There are three states of validity in the license certificate solution. A license can be in one of the following states:
A valid license means that all the information, such as the license holder’s name, address and etc, and the local server date/time are within the range of the start-end date/times, stored in the certificate.
An invalid license means that any one of the information is corrupted or the certificate itself does not exist in the Ethereum blockchain network.
An expired license means that all the informations are correct and the certificate do exist in the blockchain network, except that the local server date/time is out of the range of the start-end date/time stored in the certificate.