Did you tried to debug?
First check if the date was fetched correctly in string format.
Then check if the casting to datetime was correct such that you didn't loose the time
Lastly, use the Dates toLongDateTimeString() proerty if needed.
drow.item("RegistrationDate") = dt.date
Here after dt, press the dot and check for available properties to get date string. Further, once the string is casted to datetime, you can specify specific format to present the datetime.