
The incorrect date is:
A.) 31 April
Because April has only 30 days, so April 31st does not exist.
All the others are correct:
-
30 June → correct
-
28 February → correct (non-leap year)
-
31 August → correct
So the wrong one is A.

The incorrect date is:
Because April has only 30 days, so April 31st does not exist.
All the others are correct:
30 June → correct
28 February → correct (non-leap year)
31 August → correct
So the wrong one is A.