gistfile1.sql

create or replace function to_char2(v_timestamp interval, v_format varchar) returns text as $$
	declare
		tmp_date varchar;
	begin
		select to_char(v_timestamp, v_format) into tmp_date;
		if found then
			select 
				cast(cast(extract(epoch from v_timestamp) / 3600 as int) as varchar) ||
				substring(tmp_date from 3) into tmp_date;
				return tmp_date;
		end if;
		return NULL;
	end;
$$ language plpgsql;