Conditions for Casts to GeometryCollection •For a number consisting of one or two digits, or for a string which can be interpeted as such a number, return a  YEAR  value as follows: •If the number is in the range 1-69 inclusive, add 2000 and return the sum. •If the number is in the range 70-99 inclusive, add 1900 and return the sum. •For a string which evaluates to 0, return 2000. •For the number 0, return 0. •For a  DATE ,  DATETIME , or  TIMESTAMP  value, return the  YEAR  portion of the value. For a  TIME value, return the current year. •If the argument is of type  DECIMAL ,  DOUBLE ,  DECIMAL , or  REAL , round the value to the nearest integer, then attempt to cast the value to  YEAR  using the rules for integer values, as shown here: •An argument of type  GEOMETRY  cannot be converted to  YEAR . •For a value that cannot be successfully converted to  YEAR , return  NULL . A string value containing non-numeric characters which must be truncated prior to conversion raises a warning, as shown here: If you do not specify the type of a  TIME  argument, you may get a different result from what you expect, as shown here: 2246 mysql>  SELECT CONVERT("11:35:00", YEAR), CONVERT(TIME "11:35:00", YEAR); mysql>  SELECT CONVERT(1944.35, YEAR), CONVERT(1944.50, YEAR); mysql>  SELECT CONVERT(66.35, YEAR), CONVERT(66.50, YEAR); 1 row in set (0.00 sec) mysql>  SHOW WARNINGS; mysql>  SELECT CONVERT("1979aaa", YEAR); +--------------------------+ | CONVERT("1979aaa", YEAR) | +--------------------------+ | 1979 | +--------------------------+ 1 row in set, 1 warning (0.00 sec) +---------+------+-------------------------------------------+ | Level | Code | Message | +---------+------+-------------------------------------------+ +----------------------+----------------------+ | CONVERT(66.35, YEAR) | CONVERT(66.50, YEAR) | +----------------------+----------------------+ | 2066 | 2067 | +----------------------+----------------------+ +------------------------+------------------------+ | CONVERT(1944.35, YEAR) | CONVERT(1944.50, YEAR) | +------------------------+------------------------+ | 1944 | 1945 | +------------------------+------------------------+ 1 row in set (0.00 sec) +---------------------------+--------------------------------+ | CONVERT("11:35:00", YEAR) | CONVERT(TIME "11:35:00", YEAR) | +---------------------------+--------------------------------+ | 2011 | 2020 | +---------------------------+--------------------------------+