MYSQL returning out of bounds date

I am doing the following query:

select
    * 
from
    `users_stuff` 
where
    (
        `status` >= '8' 
        and `start` between '2017-07-01' and '2017-07-11' 
        and `outside_url` is not null 
        and (
            `param1` = '1' 
            and `param2` = 'A'
        ) 
        or (
            `param1` = '0' 
            and `param2` = 'B'
        ) 
        and `user_id` = '14' 
        and `external_id` is not null
    ) 
    and `deleted_at` is null

however when the results are returned to me I see items with the "start" set to the 12th of July. Why is that? What is wrong here that would cause that?

Thanks!

via Chebli Mohamed