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10.3.1 The DATETIME, DATE, and TIMESTAMP Types »
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10.3. Date and Time Types

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10.3.1. The DATETIME, DATE, and TIMESTAMP Types
10.3.2. The TIME Type
10.3.3. The YEAR Type
10.3.4. Year 2000 Issues and Date Types

The date and time types for representing temporal values are DATETIME, DATE, TIMESTAMP, TIME, and YEAR. Each temporal type has a range of legal values, as well as a “zero” value that is used when you specify an illegal value that MySQL cannot represent. The TIMESTAMP type has special automatic updating behavior, described later on. For temporal type storage requirements, see Section 10.5, “Data Type Storage Requirements”.

MySQL versions through 4.1 accept certain “illegal” values for dates, such as '2009-11-31'. This is useful when you want to store a possibly incorrect value specified by a user (for example, in a web form) in the database for future processing. MySQL verifies only that the month is in the range from 0 to 12 and that the day is in the range from 0 to 31. These ranges are defined to include zero because MySQL allows you to store dates where the day or month and day are zero in a DATE or DATETIME column. This is extremely useful for applications that need to store a birthdate for which you do not know the exact date. In this case, you simply store the date as '2009-00-00' or '2009-01-00'. If you store dates such as these, you should not expect to get correct results for functions such as DATE_SUB() or DATE_ADD() that require complete dates.

MySQL also allows you to store '0000-00-00' as a “dummy date.” This is in some cases more convenient (and uses less data and index space) than storing NULL values.

Here are some general considerations to keep in mind when working with date and time types:

  • MySQL retrieves values for a given date or time type in a standard output format, but it attempts to interpret a variety of formats for input values that you supply (for example, when you specify a value to be assigned to or compared to a date or time type). Only the formats described in the following sections are supported. It is expected that you supply legal values. Unpredictable results may occur if you use values in other formats.

  • Dates containing two-digit year values are ambiguous because the century is unknown. MySQL interprets two-digit 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.

  • Although MySQL tries to interpret values in several formats, dates always must be given in year-month-day order (for example, '98-09-04'), rather than in the month-day-year or day-month-year orders commonly used elsewhere (for example, '09-04-98', '04-09-98').

  • MySQL automatically converts a date or time type value to a number if the value is used in a numeric context and vice versa.

  • By default, when MySQL encounters a value for a date or time type that is out of range or otherwise illegal for the type (as described at the beginning of this section), it converts the value to the “zero” value for that type. The exception is that out-of-range TIME values are clipped to the appropriate endpoint of the TIME range.

    Data Type “Zero” Value
    DATETIME '0000-00-00 00:00:00'
    DATE '0000-00-00'
    TIMESTAMP (4.1 and up) '0000-00-00 00:00:00'
    TIMESTAMP (before 4.1) 00000000000000
    TIME '00:00:00'
    YEAR 0000

  • The “zero” values are special, but you can store or refer to them explicitly using the values shown in the table. You can also do this using the values '0' or 0, which are easier to write.

  • “Zero” date or time values used through MyODBC are converted automatically to NULL in MyODBC 2.50.12 and above, because ODBC cannot handle such values.