The YEAR function returns the year in the range of 1 to 9,999 from the specified parameter. You can specify DATE, TIMESTAMP, or DATETIME type; the value is returned in INTEGER type.
YEAR(date)
SELECT YEAR('2010-10-04');
year('2010-10-04')
=====================
2010
SELECT YEAR('2010-10-04 12:34:56');
year('2010-10-04 12:34:56')
==============================
2010
SELECT YEAR('2010-10-04 12:34:56.7890');
year('2010-10-04 12:34:56.7890')
===================================
2010
SELECT YEAR('12:34:56');
ERROR: Conversion error in date format.