Extract Date Portion Only From DateTime Field
You can check for the daily boundaries i.e. between the begining of the day at 00:00 and the begining of the next day at 00:00.

Query:

DECLARE @date datetime = '20160301'

SELECT *
FROM #Bbb
WHERE datetime1 &gt;= @date AND datetime1 &lt; DATEADD(day, 1, @date)
;


Or this WHERE clause for dates on a given day or later:

WHERE datetime1 &gt;= @date


Output:

id  | datetime1
1   | 2016-03-01 17:35:19.000
2   | 2016-03-01 18:44:15.000


You can also remove the TIME part (set it to 00:00:00.000) with this query:

DECLARE @date datetime = getdate()
SELECT @date, DATEADD(day, DATEDIFF(day, 0, @date), 0);


However using functions will limit index usage.

Ouput:

datetime                | date
2016-03-09 14:40:25.080 | 2016-03-09 00:00:00.000