Deadline
The final date or time by which a task or project must be completed.
In practice
A deadline is the fixed point by which work must be finished. In design it shapes the whole process: how many concepts can be explored, how many rounds of feedback fit, and when files must reach the printer or developer. A brochure due on Friday often has an earlier real deadline for print-ready files, sometimes several days before, and designers plan backward from it.
Often confused with milestone
A deadline is the final completion date; a milestone is an intermediate checkpoint along the way, such as concept approval.
Try this
Take a deadline you face and plan backward, writing the date by which each step must be finished.