All Evidence create pages (for Dynamic and Non-Dynamic Evidence Types) have a Received Date field which defaults to the current date. The received date marks the start of the period for which the Case Evidence record will be active, and is a mandatory field.
For Non-Dynamic Evidence Types, case workers can (unless custom validations preclude it) enter any date they choose as the received date. Dynamic Evidence however imposes some limitations on this. One such limitation is that the Received Date may not be before the Effective Date of the earliest version of the Dynamic Evidence Type. In effect, a Case Evidence record cannot be valid before the Dynamic Evidence Type itself is valid, which makes sense.
The above begs the question: if several Versions of the Dynamic Evidence Type for which the Case Evidence is being created exist, how does the system know which one is being created, and hence which user interface to present to the user? The system will always initially present the user interface for creating the Version of the Dynamic Evidence Type that is Active on the current date.
If the user, while creating the Case Evidence record, modifies the Received Date so that it falls in a time period where a different Dynamic Evidence Type Version is Active, then the system will redirect the user to the appropriate user interface for the correct Dynamic Evidence Type Version. The data that the user has already entered will be pre-populated on the page to which the user is redirected.
Therefore, the Received Date field is effectively the key to determining the Dynamic Evidence Type Version in respect of which the Case Evidence record is created. The caseworker user should not have to concern themselves with this - they simply consider the business meaning of the date and the system will present them with the appropriate user interface for creating the Case Evidence structure that applies at that point in time.