Syntax:
FROM_UNIXTIME(unix_timestamp), FROM_UNIXTIME(unix_timestamp,format)

Returns a representation of the unix_timestamp argument as a value in
'YYYY-MM-DD HH:MM:SS' or YYYYMMDDHHMMSS.uuuuuu format, depending on
whether the function is used in a string or numeric context. The value
is expressed in the current time zone. unix_timestamp is an internal
timestamp value such as is produced by the UNIX_TIMESTAMP() function.

If format is given, the result is formatted according to the format
string, which is used the same way as listed in the entry for the
DATE_FORMAT() function.

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

