Your parameter 'Date' has a datatype of date which you've currently set to Range which is why it's a slider. Change 'allowable values' to all and it will become a calendar control or change it to 'List', specify a list of allowable dates and it will be a dropdown.
Thank you so much for the response.
The reason i used the parameter as a Date is i am using this parameter as a rolling sum and the rolling sum is calculated dynamic based on the slider selected date(month and year) which is what my requirement is.
Now my end users want it to be a drop down instead of slider which is where i hit the road block.
Like I said in my previous post, you need to change the allowable values option of the parameter.