How to convert from date to datetime with midnight as time?

I have a minimum time and a maximum time.  They are being returned as a date without a time component.  I need the minimum time to be changed to a datetime where the time is one second past midnight and the maximum time is the date and 1 second before 1:00 AM but it needs to be in 24 hour format.
I've had no luck with CDate and DateTime.Parse or DateTime.ParseExact.  They all either hang and don't return or complain that 00 is not a valid hour.
dStartInterval has this value at the time of the value check; #8/13/2013#
My latest effort looks like this:
        If dStartInterval.Hour = 0 Then             sTempdatestring = dStartInterval.Day & "/" & dStartInterval.Month & "/" & dStartInterval.Year & " 12:00:01 AM"         Else           ...