- 11.3 Date and Time Types
- 11.3.1 The DATE, DATETIME, and TIMESTAMP Types
- 11.3.2 The TIME Type
- 11.3.3 The YEAR Type
- 11.3.4 YEAR(2) Limitations and Migrating to YEAR(4)
- 11.3.5 Automatic Initialization and Updating for TIMESTAMP
- 11.3.6 Fractional Seconds in Time Values
- 11.3.7 Conversion Between Date and Time Types
- 11.3.8 Two-Digit Years in Dates
The DATE, DATETIME, and
TIMESTAMP types are related. This section
describes their characteristics, how they are similar, and how
they differ. MySQL recognizes DATE,
DATETIME, and TIMESTAMP
values in several formats, described in
Section 9.1.3, “Date and Time Literals”. For the
DATE and DATETIME range
descriptions, “supported” means that although
earlier values might work, there is no guarantee.
The DATE type is used for values with a date
part but no time part. MySQL retrieves and displays
DATE values in
'YYYY-MM-DD' format. The supported range is
'1000-01-01' to
'9999-12-31'.
The DATETIME type is used for values that
contain both date and time parts. MySQL retrieves and displays
DATETIME values in 'YYYY-MM-DD
HH:MM:SS' format. The supported range is
'1000-01-01 00:00:00' to '9999-12-31
23:59:59'.
The TIMESTAMP data type is used for values
that contain both date and time parts.
TIMESTAMP has a range of '1970-01-01
00:00:01' UTC to '2038-01-19
03:14:07' UTC.
MySQL converts TIMESTAMP values from the
current time zone to UTC for storage, and back from UTC to the
current time zone for retrieval. (This does not occur for other
types such as DATETIME.) By default, the
current time zone for each connection is the server's time. The
time zone can be set on a per-connection basis. As long as the
time zone setting remains constant, you get back the same value
you store. If you store a TIMESTAMP value,
and then change the time zone and retrieve the value, the
retrieved value is different from the value you stored. This
occurs because the same time zone was not used for conversion in
both directions. The current time zone is available as the value
of the time_zone system
variable. For more information, see
Section 10.6, “MySQL Server Time Zone Support”.
The TIMESTAMP data type offers automatic
initialization and updating to the current date and time. For
more information, see
Section 11.3.5, “Automatic Initialization and Updating for
TIMESTAMP”.
A DATETIME or TIMESTAMP
value can include a trailing fractional seconds part in up to
microseconds (6 digits) precision. Although this fractional part
is recognized, it is discarded from values stored into
DATETIME or TIMESTAMP
columns. For information about fractional seconds support in
MySQL, see Section 11.3.6, “Fractional Seconds in Time Values”.
Invalid DATE, DATETIME, or
TIMESTAMP values are converted to the
“zero” value of the appropriate type
('0000-00-00' or '0000-00-00
00:00:00').
Be aware of certain properties of date value interpretation in MySQL:
MySQL permits a “relaxed” format for values specified as strings, in which any punctuation character may be used as the delimiter between date parts or time parts. In some cases, this syntax can be deceiving. For example, a value such as
'10:11:12'might look like a time value because of the “:” delimiter, but is interpreted as the year'2010-11-12'if used in a date context. The value'10:45:15'is converted to'0000-00-00'because'45'is not a valid month.The server requires that month and day values be valid, and not merely in the range 1 to 12 and 1 to 31, respectively. With strict mode disabled, invalid dates such as
'2004-04-31'are converted to'0000-00-00'and a warning is generated. With strict mode enabled, invalid dates generate an error. To permit such dates, enableALLOW_INVALID_DATES. See Section 5.1.7, “Server SQL Modes”, for more information.MySQL does not accept
TIMESTAMPvalues that include a zero in the day or month column or values that are not a valid date. The sole exception to this rule is the special “zero” value'0000-00-00 00:00:00'.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
00-69are converted to2000-2069.Year values in the range
70-99are converted to1970-1999.
The MySQL server can be run with the
MAXDB SQL mode enabled. In
this case, TIMESTAMP is identical with
DATETIME. If this mode is enabled at the
time that a table is created, TIMESTAMP
columns are created as DATETIME columns. As
a result, such columns use DATETIME display
format, have the same range of values, and there is no
automatic initialization or updating to the current date and
time. See Section 5.1.7, “Server SQL Modes”.
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User Comments
You can automatically convert an invalid date to the valid equivalent like this:
SELECT '2008-02-31' + INTERVAL 0 DAY;
# 2008-03-02
This lets you avoid storing invalid dates without bothering the user and without having to manually program a fix into your app. I suppose in >=5.0.2, you'd have to enable ALLOW_INVALID_DATES to avoid having it converted to '0000-00-00'. This also works with DATETIMEs.
In addition to Linus Rachlis,
if you add 0 month to an invalid date, you could get last day of the month, for example
SELECT '2008-02-31' + INTERVAL 0 MONTH;
# 2008-02-29
It works as
SELECT LAST_DAY('2008-02-31');
# 2008-02-29
even we can add a trigger to check a valid date so that it atomatically changes to correct date
A possible problem that can happen with date_format and ORDER/GROUP BY is explained at http://www.geeksww.com/tutorials/database_management_systems/mysql/tips_and_tricks/mysql_dateformat_function_and_order_by.php
Please note that year restriction of 1000-9999 appears to be in place in versions 5.0.2+. The wording of this documentation doesn't make it clear whether or not this year restriction remained in place.
The ODBC driver at least seems to enforce the restriction by bombing out when exporting a year such as 193/08/17.
The 5.0.2 change appears to add an additional validity check and not replace any existing restrictions.