When deals with various time-based events, activities, etc. of the intended solution.
These are examples of the kinds of questions you should be asking with respect to the “When” of the intended solution:
When does the solution need to be ready for launching?
When do users need to be able to perform specific activities?
When do periodic activities need to be performed (e.g., daily, weekly, monthly, quarterly, yearly, etc.)?
When does the solution need to be available for use (normal business hours, 24/7/365, etc.)?
When can or should the solution be unavailable?
Do any activities need a history trail captured?
When can data be purged from the solution?