How to set a default for a report plugin parameter of type date?

I have a report plugin that has a date parameter. How do I set the default? I’ve tried different formats for the date but none seem to work.

The atlassian-plugin.xml file contains this entry:

referenceSprintStartDate
Reference Sprint Start Date:

The start date of the reference sprint. All future sprints
will start the same day of the week in two week intervals.

date
17/Mar/23