can’t get query to order posts by acf datepicker

I’ve read alot, I’ve tried a bunch of different things, I still can’t get my query to order posts by acf’s datepicker field. This is what my code looks like:

$args = array(
    'post_type'   =>  'arm_careers',
    'post_status' => 'publish',
    'posts_per_page' => -1,
    'meta_key' => 'post_date',
    'orderby' => 'meta_value_num',
    'meta_type' => 'DATE',
    'order' => 'ASC',
);

I’m not using PRO, I’m using the free one. The save format is yymmdd, I’ve also tried YYYYMMDD but neither worked.

Here is what it currently looks like:
August 14, 2018
August 2, 2018
August 9, 2018

when I want it to look like:
August 2, 2018
August 9, 2018
August 14, 2018

The display format is MM d, yy.

You need to convert your saved format to the post_date format which is in

Y-m-d H:i:s

Only then will the comparators work properly with automatically generated query objects.