How would you ensure a user enters a date of birth in the past on a job application form?

Utilizing a validate rule to ensure that a user enters a date of birth in the past is the most effective choice because validate rules are specifically designed for input validation during form submissions. By applying a validate rule, you can establish conditions that the input must satisfy before the form can be successfully submitted.

In this case, the validate rule can be structured to check that the date of birth entered is less than the current date, effectively enforcing the requirement that the date provided must be a past date. This ensures that the rule is triggered whenever there is user input, providing immediate feedback if the input does not meet the specified criteria.

Other methods, such as using a calendar control, might provide a user-friendly way of selecting dates but do not inherently validate the selected date against business rules. A when condition could be useful for controlling the visibility of fields or sections based on certain criteria but does not directly validate user input. Similarly, a declare expression is more suited for calculated fields or maintaining data integrity rather than enforcing input validation rules. Hence, the validate rule is the most appropriate and direct approach for ensuring the date of birth is entered correctly.