How to pass all test cases in Datetime Boundary testing challenge?

I did a testing challenge at http://testingchallenges.thetestingmap.org/challenge6.php#.

I've passed 13 out of 16 test cases. At the 14th test case, the hint is "What happens in March? (lowest hour and time that does not exist)", and I have no idea. Please help me what is the date and time that is invalid in this test case. Thanks