2-Digit Years in Dates Suppose that the current date is  ’2012-01-01’ .  TIME  values of  ’12:00:00’ ,  ’24:00:00’ , and  ’-12:00:00’ , when converted to  DATETIME  or  TIMESTAMP  values, result in  ’2012-01-01 12:00:00’ ,  ’2012-01-02 00:00:00’ , and  ’2011-12-31 12:00:00’ , respectively. Conversion of  TIME  to  DATE  is similar but discards the time part from the result:  ’2012-01-01’ , ’2012-01-02’ , and  ’2011-12-31’ , respectively. Explicit conversion can be used to override implicit conversion. For example, in comparison of  DATE and  DATETIME  values, the  DATE  value is coerced to the  DATETIME  type by adding a time part of ’00:00:00’ . To perform the comparison by ignoring the time part of the  DATETIME  value instead, use the  CAST()  function in the following way: Conversion of  TIME  and  DATETIME  values to numeric form (for example, by adding  +0 ) depends on whether the value contains a fractional seconds part.  TIME( N )  or  DATETIME( N )  is converted to integer when  N  is 0 (or omitted) and to a  DECIMAL  value with  N  decimal digits when  N  is greater than 0: Date values with 2-digit years are ambiguous because the century is unknown. Such values must be interpreted into 4-digit form because MySQL stores years internally using 4 digits. For  DATETIME ,  DATE , and  TIMESTAMP  types, MySQL interprets dates specified with ambiguous year values using these rules: For  YEAR , the rules are the same, with this exception: A numeric  00  inserted into  YEAR  results in  0000 rather than  2000 . To specify zero for  YEAR  and have it be interpreted as  2000 , specify it as a string  ’0’  or ’00’ . Remember that these rules are only heuristics that provide reasonable guesses as to what your data values mean. If the rules used by MySQL do not produce the values you require, you must provide unambiguous input containing 4-digit year values. ORDER BY  properly sorts  YEAR  values that have 2-digit years. Some functions like  MIN()  and  MAX()  convert a  YEAR  to a number. This means that a value with a 2-digit year does not work properly with these functions. The fix in this case is to convert the  YEAR  to 4-digit year format. 11.3 String Data Types 11.2.8 2-Digit Years in Dates date_col  = CAST( datetime_col  AS DATE) mysql>  SELECT CURTIME(), CURTIME()+0, CURTIME(3)+0; mysql>  SELECT NOW(), NOW()+0, NOW(3)+0; +-----------+-------------+--------------+ | CURTIME() | CURTIME()+0 | CURTIME(3)+0 | +-----------+-------------+--------------+ | 09:28:00 | 92800 | 92800.887 | +-----------+-------------+--------------+ +---------------------+----------------+--------------------+ | NOW() | NOW()+0 | NOW(3)+0 | +---------------------+----------------+--------------------+ | 2012-08-15 09:28:00 | 20120815092800 | 20120815092800.889 | +---------------------+----------------+--------------------+ •Year values in the range  00-69  become  2000-2069 . •Year values in the range  70-99  become  1970-1999 . 2034