When you need something like that on server side, you usually create a table which contains all possible dates between two points in time, and then left join this table with query results. Something like this:
create procedure sp1(d1 date, d2 date)
declare d datetime;
create temporary table foo (d date not null);
set d = d1
while d <= d2 do
insert into foo (d) values (d)
set d = date_add(d, interval 1 day)
end while
select foo.d, count(date)
from foo left join table on foo.d = table.date
group by foo.d order by foo.d asc;
drop temporary table foo;
end procedure
In this particular case it would be better to put a little check on the client side, if current date is not previos+1, put some addition strings.