Laravel created_at retrun object in place of date format in database?

I am trying to retrun created_at datetime from users table in JSON response in Laravel.

In my databaes it show the value as 2016-07-18 00:00:00 but when I try to return in JSON api it converts into

{
    date: "2016-07-18 00:00:00.000000",
    timezone_type: 3,
    timezone: "UTC"
}

How can I fix this problem.

via Chebli Mohamed