A more thorough explanation:

Definition: Terminus ad quem is a Latin term used in law to refer to the point to which some action must be taken.

Example: In a contract, the terminus ad quem may be the deadline for payment or the date by which a project must be completed.

This means that the terminus ad quem is the final point or deadline by which something must be done. In the example of a contract, if payment is not made by the terminus ad quem, then the contract may be considered breached and legal action may be taken. Similarly, if a project is not completed by the terminus ad quem, then there may be consequences such as penalties or termination of the contract.