SQL Query - format Date

[singabaloo]

I'm trying to run a MySQL query to list the members of a group and show the last activity date. The results gives me the date in a serial number like 1349148662

Here is my code. What do I need to add or change to format the query correctly ?

SELECT  `user`.`username` ,  `user`.`usergroupid` ,  `user`.`lastactivity` 
FROM  `user` 
WHERE (
`user`.`usergroupid` =  "7"
)
ORDER BY  `user`.`lastactivity` DESC 
LIMIT 0 , 30