This action prompts the user for a date by opening a calendar pop-up screen and letting the user select a date.
Note the distinction between this action and the Date Input Field display element. While Prompt for Date is an action used if at a certain point in the process there is a need to ask the user to enter a date, Date Input Field is not an action, but rather a display element that defines a date field within the parent display element.
You can use Prompt for Date, though, to model the behavior of a custom display element. E.g. you can define a Number Input Field display element named Week and model within it an action called <On Click>, which uses Prompt for Date to get a date from the user and then calculates the week to which this date belongs (using Get Week). All in all, this amounts to implementing a "Week Input Field" display element, which is very similar to the built-in Date Input Field
<Date> (non-repetitive date exit [required]): The selected date.