6.2.2.1 Y2K Issues and Date Types

MySQL itself is Y2K-safe (see section 1.2.5 Year 2000 Compliance), but input values presented to MySQL may not be. Any input containing 2-digit year values is ambiguous, because the century is unknown. Such values must be interpreted into 4-digit form because MySQL stores years internally using four digits.

For DATETIME, DATE, TIMESTAMP, and YEAR types, MySQL interprets dates with ambiguous year values using the following rules:

• Year values in the range 00-69 are converted to 2000-2069.
• Year values in the range 70-99 are converted to 1970-1999.

Remember that these rules provide only reasonable guesses as to what your data mean. If the heuristics used by MySQL don't produce the correct values, you should provide unambiguous input containing 4-digit year values.

ORDER BY will sort 2-digit YEAR/DATE/DATETIME types properly.

Note also that some functions like MIN() and MAX() will convert a TIMESTAMP/DATE to a number. This means that a timestamp with a 2-digit year will not work properly with these functions. The fix in this case is to convert the TIMESTAMP/DATE to 4-digit year format or use something like MIN(DATE_ADD(timestamp,INTERVAL 0 DAYS)).

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