SSRS 2010 Datepicker calendar is not displayed when a parameter has the available values setup

In a modifed ssrs 2010, I added a parameter called startdate where the data type is set to date/time.

The start date parameter obtains its default value from the following query:
select schoolyear,min(startdate)AS STARTDATE
from [CampusOps].[dbo].[AtnLtrSemester]
where schoolyear = @pSchoolYear
group by schoolyear

**Note the @pSchoolYear value is set to integer.

The query runs fine when I only have a default value set and the value displayed looks like the following 07/27/2017.
**Note the school year parameter also has a default value which is currently 2018.

The problem is when the user wants to change the school year parameter to 2017. The start date problem does not change.

To fix that issue, I have the available values set to dataset=startdate, value field=startdate, and label field=startdate.

The problem is then the datepicker calendar option that I want the user to access is not displayed when the available values of a parameter are selected.

Thus can you tell me what I can do to solve this issue?

wrong forum