11.3 Date and Time Types

The date and time types for representing temporal values are DATE, TIME, DATETIME, TIMESTAMP, and YEAR. Each temporal type has a range of valid values, as well as a “zero” value that may be used when you specify an invalid value that MySQL cannot represent. The TIMESTAMP type has special automatic updating behavior, described later. For temporal type storage requirements, see Section 11.8, “Data Type Storage Requirements”.

Keep in mind these general considerations 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). For a description of the permitted formats for date and time types, see Section 9.1.3, “Date and Time Literals”. It is expected that you supply valid values. Unpredictable results may occur if you use values in other formats.
Although MySQL tries to interpret values in several formats, date parts must always 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').
Dates containing two-digit year values are ambiguous because the century is unknown. MySQL interprets two-digit year values using these rules:
- Year values in the range 70-99 are converted to 1970-1999.
- Year values in the range 00-69 are converted to 2000-2069.
See also Section 11.3.7, “Two-Digit Years in Dates”.
Conversion of values from one temporal type to another occurs according to the rules in Section 11.3.6, “Conversion Between Date and Time Types”.
MySQL automatically converts a date or time 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 invalid for the type, 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.
By setting the SQL mode to the appropriate value, you can specify more exactly what kind of dates you want MySQL to support. (See Section 5.1.11, “Server SQL Modes”.) You can get MySQL to accept certain dates, such as '2009-11-31', by enabling the ALLOW_INVALID_DATES SQL mode. This is useful when you want to store a “possibly wrong” value which the user has specified (for example, in a web form) in the database for future processing. Under this mode, MySQL verifies only that the month is in the range from 1 to 12 and that the day is in the range from 1 to 31.
MySQL permits you to store dates where the day or month and day are zero in a DATE or DATETIME column. This is useful for applications that need to store birthdates for which you may 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. To disallow zero month or day parts in dates, enable the NO_ZERO_IN_DATE mode.
MySQL permits you to store a “zero” value of '0000-00-00' as a “dummy date.” This is in some cases more convenient than using NULL values, and uses less data and index space. To disallow '0000-00-00', enable the NO_ZERO_DATE mode.
“Zero” date or time values used through Connector/ODBC are converted automatically to NULL because ODBC cannot handle such values.

The following table shows the format of the “zero” value for each type. 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. For temporal types that include a date part (DATE, DATETIME, and TIMESTAMP), use of these values produces warnings if the NO_ZERO_DATE SQL mode is enabled.

Data Type	“Zero” Value
`DATE`	`'0000-00-00'`
`TIME`	`'00:00:00'`
`DATETIME`	`'0000-00-00 00:00:00'`
`TIMESTAMP`	`'0000-00-00 00:00:00'`
`YEAR`	`0000`

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