The DATETIME, DATE, and TIMESTAMP types are related. This section describes their characteristics, how they are similar, and how they differ.
The DATETIME type is used when you need values that contain both date and time information. 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 DATE type is used when you need only a date value, without a time part. MySQL retrieves and displays DATE values in 'YYYY-MM-DD' format. The supported range is '1000-01-01' to '9999-12-31'.
For the DATETIME and DATE range descriptions, “supported” means that although earlier values might work, there is no guarantee.
The TIMESTAMP data type has varying properties, depending on the MySQL version and the SQL mode the server is running in. These properties are described later in this section.
You can specify DATETIME, DATE, and TIMESTAMP values using any of a common set of formats:
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As a string in either
'YYYY-MM-DD HH:MM:SS'or'YY-MM-DD HH:MM:SS'format. A “relaxed” syntax is allowed: Any punctuation character may be used as the delimiter between date parts or time parts. For example,'98-12-31 11:30:45','98.12.31 11+30+45','98/12/31 11*30*45', and'98@12@31 11^30^45'are equivalent. -
As a string in either
'YYYY-MM-DD'or'YY-MM-DD'format. A “relaxed” syntax is allowed here, too. For example,'98-12-31','98.12.31','98/12/31', and'98@12@31'are equivalent. -
As a string with no delimiters in either
'YYYYMMDDHHMMSS'or'YYMMDDHHMMSS'format, provided that the string makes sense as a date. For example,'19970523091528'and'970523091528'are interpreted as'1997-05-23 09:15:28', but'971122129015'is illegal (it has a nonsensical minute part) and becomes'0000-00-00 00:00:00'. -
As a string with no delimiters in either
'YYYYMMDD'or'YYMMDD'format, provided that the string makes sense as a date. For example,'19970523'and'970523'are interpreted as'1997-05-23', but'971332'is illegal (it has nonsensical month and day parts) and becomes'0000-00-00'. -
As a number in either
YYYYMMDDHHMMSSorYYMMDDHHMMSSformat, provided that the number makes sense as a date. For example,19830905132800and830905132800are interpreted as'1983-09-05 13:28:00'. -
As a number in either
YYYYMMDDorYYMMDDformat, provided that the number makes sense as a date. For example,19830905and830905are interpreted as'1983-09-05'. -
As the result of a function that returns a value that is acceptable in a
DATETIME,DATE, orTIMESTAMPNOW()orCURRENT_DATE. context, such as
Illegal DATETIME, DATE, or TIMESTAMP values are converted to the “zero” value of the appropriate type ('0000-00-00 00:00:00' or '0000-00-00').
For values specified as strings that include date part delimiters, it is not necessary to specify two digits for month or day values that are less than 10. '1979-6-9' is the same as '1979-06-09'. Similarly, for values specified as strings that include time part delimiters, it is not necessary to specify two digits for hour, minute, or second values that are less than 10. '1979-10-30 1:2:3' is the same as '1979-10-30 01:02:03'.
Values specified as numbers should be 6, 8, 12, or 14 digits long. If a number is 8 or 14 digits long, it is assumed to be in YYYYMMDD or YYYYMMDDHHMMSS format and that the year is given by the first 4 digits. If the number is 6 or 12 digits long, it is assumed to be in YYMMDD or YYMMDDHHMMSS format and that the year is given by the first 2 digits. Numbers that are not one of these lengths are interpreted as though padded with leading zeroes to the closest length.
Values specified as non-delimited strings are interpreted using their length as given. If the string is 8 or 14 characters long, the year is assumed to be given by the first 4 characters. Otherwise, the year is assumed to be given by the first 2 characters. The string is interpreted from left to right to find year, month, day, hour, minute, and second values, for as many parts as are present in the string. This means you should not use strings that have fewer than 6 characters. For example, if you specify '9903', thinking that represents March, 1999, MySQL inserts a “zero” date value into your table. This occurs because the year and month values are 99 and 03, but the day part is completely missing, so the value is not a legal date. However, you can explicitly specify a value of zero to represent missing month or day parts. For example, you can use '990300' to insert the value '1999-03-00'.
You can to some extent assign values of one date type to an object of a different date type. However, there may be some alteration of the value or loss of information:
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If you assign a
DATEvalue to aDATETIMEorTIMESTAMPobject, the time part of the resulting value is set to'00:00:00'because theDATEvalue contains no time information. -
If you assign a
DATETIMEorTIMESTAMPvalue to aDATEobject, the time part of the resulting value is deleted because theDATEtype stores no time information. -
Remember that although
DATETIME,DATE, andTIMESTAMPvalues all can be specified using the same set of formats, the types do not all have the same range of values. For example,TIMESTAMPvalues cannot be earlier than1970or later than2037. This means that a date such as'1968-01-01', while legal as aDATETIMEorDATEvalue, is not valid as aTIMESTAMPvalue and is converted to0.
Be aware of certain pitfalls when specifying date values:
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The relaxed format allowed for values specified as strings can be deceiving. For example, a value such as
'10:11:12'might look like a time value because of the ‘:’ delimiter, but if used in a date context is interpreted as the year'2010-11-12'. The value'10:45:15'is converted to'0000-00-00''45'is not a legal month. because -
As of 5.0.2, the server requires that month and day values be legal, 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 allow such dates, enableALLOW_INVALID_DATES. See Section 5.2.5, “The Server SQL Mode”, for more information.Before MySQL 5.0.2, the MySQL server performs only basic checking on the validity of a date: The ranges for year, month, and day are 1000 to 9999, 00 to 12, and 00 to 31, respectively. Any date containing parts not within these ranges is subject to conversion to
'0000-00-00'. Please note that this still allows you to store invalid dates such as'2002-04-31'. To ensure that a date is valid, you should perform a check in your application. -
Dates containing two-digit year values are ambiguous because the century is unknown. MySQL interprets two-digit year values using the following rules:
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Year values in the range
00-69are converted to2000-2069. -
Year values in the range
70-99are converted to1970-1999.
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