postgresql - how to sort on date using group by statement

I'm trying to do a count of hits per day. The query does the counts as needed, however my days are not in order. How can I fix this?

hittime not converted is a timestamp -2016-06-16 06:57:14

Here's the query:

select  to_char(hittime, 'YYYY-MM-DD'), 
        count(hitid) 
from    hits 
group by to_char(hittime, 'YYYY-MM-DD');

Sample output:

 to_char   | count
------------+-------
 2016-05-04 |    92
 2016-05-05 |   120
 2016-05-07 |     2
 2016-05-08 |     2
 2016-05-11 |   139
 2016-05-13 |    54
 2016-05-17 |    96
 2016-05-18 |    23
 2016-05-26 |    53
 2016-05-28 |     1
 2016-05-30 |    31
 2016-06-04 |     9
 2016-06-05 |    37
 2016-06-06 |   173
 2016-06-09 |   364
 2016-06-13 |   446
 2016-06-14 |   533
 2016-06-16 |    10
 2016-05-06 |   153
 2016-05-09 |   297
 2016-05-10 |    90
 2016-05-12 |    88
 2016-05-16 |    66
 2016-05-19 |   123
 2016-05-20 |    34