A coworker ran into this problem, found the solution, and sent it to all of our EG users. I had to follow up and let them know that the parameter must be in double quotes. You may want to add that to the Note. Users that have only used EG may not know that.
Problem Note 18260: Errors might occur when using a date parameter in a stored process in SAS Enterprise Guide
If you attempt to create a stored process in SAS Enterprise Guide on a
task that uses a parameter defined with a data type of Date, you might
see the following message:
Parameter Translation Problems.
The following problems were encountered mapping project parameters
to stored process parameters.
The parameter 'date_parameter_name' is defined to be enclosed in
quotes; however, this is not supported by the stored process
To circumvent the problem, on page 2 of 8 in the Create New SAS Stored
Process Wizard, edit the reference to the date parameter. For example,