### Using built-in functions to set date and time parameter values

For a parameter of the Date, DateTime, or Time type, you can customize a dynamic date and time value by creating an expression using built-in formula functions.

To do this:

1. In the places where you are able to specify a value for the parameter, you may see the calendar button . Click this button and the Calendar dialog appears. See the dialog.

2. The Template drop-down list on the right provides some predefined expressions for you to use. You can customize your own expression either based on an existing template or by directly editing the contents in the Expression text box.

   If you cannot see the Template label on the right, click >> on the bottom left corner.

3. JReport's built-in Date/Time formula functions are available for inserting into your expression. To make use of them, click and the Expression dialog appears. See the dialog.

4. The top text box shows the current expression statement. Expand the Date/Time node below, double-click the required function to insert it where the cursor is located in the expression. Upon finishing, click OK to return to the Calendar dialog.
5. The Preview box calculates the result of the current expression. Each time you modify the expression, you can click in the box to refresh the result. If it is an invalid expression, an error message will be shown in the box and no change will be made to the calendar and the currently selected date/time will be remained in the calendar.
6. When done, click OK to add the value.