TIMESTAMP

A timestamp. The range is '1970-01-01 00:00:01' UTC to '2038-01-09
03:14:07' UTC. TIMESTAMP values are stored as the number of seconds
since the epoch ('1970-01-01 00:00:00' UTC). A TIMESTAMP cannot
represent the value '1970-01-01 00:00:00' because that is equivalent to
0 seconds from the epoch and the value 0 is reserved for representing
'0000-00-00 00:00:00', the "zero" TIMESTAMP value.

A TIMESTAMP column is useful for recording the date and time of an
INSERT or UPDATE operation. By default, the first TIMESTAMP column in a
table is automatically set to the date and time of the most recent
operation if you do not assign it a value yourself. You can also set
any TIMESTAMP column to the current date and time by assigning it a
NULL value. Variations on automatic initialization and update
properties are described in
http://dev.mysql.com/doc/refman/5.1/en/timestamp.html.

A TIMESTAMP value is returned as a string in the format 'YYYY-MM-DD
HH:MM:SS' with a display width fixed at 19 characters. To obtain the
value as a number, you should add +0 to the timestamp column.

*Note*: The TIMESTAMP format that was used prior to MySQL 4.1 is not
supported in MySQL 5.1; see MySQL 3.23, 4.0, 4.1 Reference Manual for
information regarding the old format.

URL: http://dev.mysql.com/doc/refman/5.1/en/date-and-time-type-overview.html

