postgres age function

select dob,extract(year from AGE(dob                  )) from dob_table limit 1;
select dob,extract(year from AGE(now(), dob           )) from dob_table limit 1;
select dob,extract(year from AGE(current_timestamp,dob)) from dob_table limit 1;
select dob,extract(year from AGE('2009-09-10', dob    )) from dob_table limit 1;
select dob,to_char(AGE(dob),'YYYY')::integer             from dob_table limit 1;
select dob,substr(AGE(dob)::text,1,3)                    from dob_table limit 1;