TRUNC of a Day and Hour is not fetching the expected output in Hive

Trunc function for the Day and for an Hour is not fetching the expected result in Hive.

However rest of the string units like 'MM', 'YYYY' works as expected

I tried the below in Hive

Query :
SELECT TRUNC('2016-12-11 01:02:04','DD') FROM sample_08;

SELECT TRUNC('2016-12-11 01:02:04','HH24') FROM sample_08;

Result:
NULL

Expectation:
Ideally it should be 2016-12-11 00:00:00 for day
2016-12-11 01:00:00 for Hour

Thanks,
Vnoth R