   TIMESTAMP[(M)]

A timestamp.  The range is '1970-01-01 00:00:00' to partway through the
year 2037.

A TIMESTAMP column is useful for recording the date and time of an
INSERT or UPDATE operation. The first TIMESTAMP column
in a table is automatically set to the date and time of the most recent
operation if you don't assign it a value yourself.  You can also set any
TIMESTAMP column to the current date and time by assigning it a
NULL value.

From MySQL 4.1 on, TIMESTAMP is returned as a string with the format
'YYYY-MM-DD HH:MM:SS'. If you want to obtain the value as a number,
you should add +0 to the timestamp column. Different timestamp
display widths are not supported.

In MySQL 4.0 and earlier, TIMESTAMP values are displayed in
YYYYMMDDHHMMSS, YYMMDDHHMMSS, YYYYMMDD, or YYMMDD
format, depending on whether M is 14 (or missing), 12,
8, or 6, but allows you to assign values to TIMESTAMP
columns using either strings or numbers.
The M argument affects only how a TIMESTAMP column is displayed,
not storage.  Its values always are stored using four bytes each.
From MySQL 4.0.12, the --new option can be used
to make the server behave as in MySQL 4.1.

Note that TIMESTAMP(M) columns where M is 8 or 14 are reported to
be numbers, whereas other TIMESTAMP(M) columns are reported to be
strings.  This is just to ensure that you can reliably dump and restore
the table with these types.
