Updating timestamps

Is it possible to update a timestamp with Postgresql?


I've looked around with google and it looks as though this should work:


exec sql begin declare section;
char api[18];
char    expiration_time[80];
exec sql end declare section;


memcpy(api, ap->api, sizeof(api));
sprintf(expiration_time, "%s + \"interval\"('0.01sec')",
ap->expiration_time);


puts(expiration_time);


exec sql update accesspoint
        set sequence_number = expiration_time = :expiration_time,
        where api = :api;


However, I just get this:
2005-08-02 10:37:41.198479 + "interval"('0.01sec')
'ERROR:  invalid input syntax for type timestamp: "2005-08-02 10:37:4

-Nigel