Assuming you have the two dates in variables named @currDate and @prevDate. Further assuming there are no deleted or new records. Even further assuming that col2 is not null.
select curr.col1, curr.col2 as col2_curr, prev.col2 as col2_prev
from [table] curr
inner join [table] prev on prev.col1 = curr.col1
where curr.date = @currDate
and prev.date = @prevDate
and curr.col2 <> prev.col2