I’m just working on setting up a custom WordPress archive for a client at the moment (displaying posts by academic year).

In order to do things absolutely right (and in case they decide to post-publish older items), I need to be able to check when the first post was published on their WordPress installation.

I figured I’d share the code out here in case someone else finds it useful (and in case anyone can suggest improvements to the code). I’ve wrapped it up as a function so you can throw it your functions.php if it’s something you’ll re-use.

/**
 * Get First Post Date Function
 *
 * @param  $format Type of date format to return, using PHP date standard, default Y-m-d
 * @return Date of first post
 */
function ax_first_post_date($format = "Y-m-d") {
 // Setup get_posts arguments
 $ax_args = array(
 'numberposts' => -1,
 'post_status' => 'publish',
 'order' => 'ASC'
 );

 // Get all posts in order of first to last
 $ax_get_all = get_posts($ax_args);

 // Extract first post from array
 $ax_first_post = $ax_get_all[0];

 // Assign first post date to var
 $ax_first_post_date = $ax_first_post->post_date;

 // return date in required format
 $output = date($format, strtotime($ax_first_post_date));

 return $output;
}

To echo it anywhere on your site just run:

echo ax_first_post_date();

I’m hoping to be a little better at keeping track of useful WordPress functions that could be reused, so have created a sub-category of my WordPress category called “Functions”. If nothing else it will be a useful reference point for me.

Update

As soon as I hit publish I knew I should have held off until I added in a date format parameter. I’ve updated the code now so that you can tell the function what format the date should be returned in (using standard PHP date format).