How do I migrate dates? In my Drupal 7 site, the date is stored in the database as 2020-08-10 00:00:00.
When I migrate those dates without any formatting (field_blog_post_date: field_blog_post_date), the date is migrated into the Drupal 8 table with the same exact formatting. However, it doesn't show when a node is viewed.
I tried to use a format_date plugin.
field_blog_post_date: 
  plugin: format_date
  source: field_blog_post_date
  from_format: 'Y-m-d H:i:s'
  to_format: 'Y-m-d'

When I use it, it causes the following error.

DateTime::createFromFormat() expects parameter 2 to be string, array given
DateTimePlus.php:251
this worked! found the answer here https://www.drupal.org/project/drupal/issues/2923723#comment-12343660
 field_blog_post_date: 
        plugin: iterator
        source: field_blog_post_date
        process:
          value:
            plugin: substr
            source: value
            start: 0
            length: 10