Storing/querying custom date data

Question

I'm currently building a site where I need to filter/order/query a custom post type by date data. I can't use the post published date for this, but can't decide what would be the most efficient way to attach this to a post for further querying/filtering on the front-end of the site.

As far as I can see my options are either:

1 - Store as custom field (probably in UNIX timestamp format) I can see that this would work, but I have concerns about scalability with this as the number of posts grows (into thousands potentially) - as all posts would have to be queried to search/filter by custom field... this doesn't seem like it would be too efficient.

2 - Store as a taxonomy (Year->month->day) I have a custom plugin I've written to pre-populate terms of a taxonomy, so have no problems modifying this a-little to setup the terms ready for Year (parent) -> month (child) -> day (grand-child) for a few years to come! In my mind this seems like it would build more efficient queries in the future? At face-value this feels a-little strange to do it like this, but I think it would produce much more efficient queires and filtering of posts on the front-end of the site, as it would be the taxonomy tables that are queried rather than custom fields in ALL of the posts.

Is this overkill? I'd very much appreciate opinions on what would work best. I should mention that from an admin point of view I have a custom post creation/editing process, so this doesn't effect my decision. I'm really just trying to figure out the best way to attach custom date data to custom post type and query against it (with certainly hundreds, if not thousands of posts!!)

Answer 1

I would store as a custom field, like you say as a timestamp or ISO 8601 (YYYY-MM-DD). That way you can leverage WP_Query's Custom Field Parameters for queries within your theme files.

For instance:

// Get posts where the custom field is less than the current time

$foo = new WP_Query(array(
  // other query vars...
  'meta_query' => array(
    array(
      'key' => 'date_custom_field',
      'value' => time(),
      'compare' => '<'
    )
  )
));

Answer 2

If you have them saved as custom meta fields you could add this into your query:

'meta_key'       => 'field_name',
'orderby'        => 'field_name'