फ़्लैशकार्ड

Both the future perfect simple and the future perfect progressive look ahead to a future reference point and evaluate earlier activity. The future perfect simple places a completed action, milestone, or quantity before that checkpoint. The future perfect progressive looks back from that same checkpoint to show how long an activity has been underway. One tense focuses on the finished product; the other focuses on the elapsed time of the process.

By opening time, we will have made twenty sandwiches.