Please help. I am trying to remove 00:00:00.0 from datetime field formula

This is the expression that I am using at the moment:

input.Customer_approval_date.addBusinessDay(15)

This is the result I get:

2017-06-21 16:00:00.0

But I don't want the time to appear. Please help :)

If the suggestion is string to remove the time, please let me know where I enter the string formula as I have seen this suggested elsewhere but don't know where to enter the code.

Thank you for your help :)