#T-SQL 37 22 bytes

Saved 15 bytes thanks to BradC's comment.

The usual hardcoded variable for lack of a stdin.

e.g.

DECLARE @ NVARCHAR(4) = '2016'

Then the solution is:

PRINT ISDATE(@+'0229')

T-SQL 37 22 bytes

Saved 15 bytes thanks to BradC's comment.

The usual hardcoded variable for lack of a stdin.

e.g.

DECLARE @ NVARCHAR(4) = '2016'

Then the solution is:

PRINT ISDATE(@+'0229')

#T-SQL 37 bytes

The usual hardcoded variable for lack of a stdin.

e.g.

DECLARE @ NVARCHAR(4) = '2016'

Then the solution is:

PRINT IIF(ISDATE(@+'0229')=1,'y','n')

#T-SQL 37 22 bytes

Saved 15 bytes thanks to BradC's comment.

The usual hardcoded variable for lack of a stdin.

e.g.

DECLARE @ NVARCHAR(4) = '2016'

Then the solution is:

PRINT ISDATE(@+'0229')

#T-SQL 37 35 bytes

The usual hardcoded variable for lack of a stdin.

e.g.

DECLARE @ NVARCHAR(4) = '2016'

Then the solution is:

PRINT IIF(ISDATE(@+0229)=1,'y','n')

Edit: Saved 2 bytes, we don't need the quotes('') in the concatenation.

#T-SQL 37 bytes

The usual hardcoded variable for lack of a stdin.

e.g.

DECLARE @ NVARCHAR(4) = '2016'

Then the solution is:

PRINT IIF(ISDATE(@+'0229')=1,'y','n')