How to us dynamic default values for this scenario

Hi Guys,

Appreciate your time looking into this:

Requirement is to have a prompt on Webi report as:

Start Date: [Date selected from calender or today] and 11:00:00 PM (note a constant Time)

End Date: [Date selected from calender or today] and 10:59:59 AM (note a constant Time)

I tried to follow the post here which is great feature in SAP BI SP6, which building prompt in Universe but got stuck

How to use new Dynamic Default Value for Universe (UNX) Prompts feature

I thought of using RelativeDate(CurrentDate();0.4583333333333333)

but CurrentDate is bad option as time varies and substraction of hours or addition of hours doesnt produce 11:00:00 PM value

Any ideas!! highly appreciate it.