I wouldn't use dateformat in the sql.
your php code where you call date() is the problem.
post all the php code that leads up to that print date() line because that would help.
you can't just do
print date("d/M/y G.i", 'unixtimestamp');
what you're doing is passing a string containing the word unixtimestamp.
your second parameter needs to be an INT, in this case an epoch timestamp.
what is the data type for the column you are retrieving?
this is what I usually do.
the timestamp column is usually an unsigned int
retrieve the data using mysql_query then loop through the results.
I usually use mysql_fetch_object, but for this I'll use mysql_fetch_assoc.
then when it comes time to print the date:
print date('d/M/y G.i',$row['timestamp_column_name']);