could be more explicit:

> **Tip**: DateTime formatters won't reproduce the same fake data if you don't fix the `$max` value:
>
>     // even when seeded, this line will return different results because $max varies
>     $faker->dateTime(); // equivalent to $faker->dateTime($max = 'now')
>     // make sure you fix the $max parameter
>     $faker->dateTime('2014-02-25 08:37:17'); // will return always the same date when seeded