Hi,
This should help you.
A.Datetime,B.Datetime
from
(select ROW_NUMBER() OVER (ORDER BY Datetime) AS RowNumber,Datetime1 from table1 ) AS A
LEFT JOIN
(select ROW_NUMBER() OVER (ORDER BY Datetime) AS RowNumber,Datetime1 from table1) AS B
ON B.RowNumber = A.RowNumber+1
Please mark it as answer if it helps.