Changing the post date and time with function

Question

What function can be used to update a post's post date and time to the current date & time?

Answer 1

Call wp_update_post() with a special value for 'post_date' and 'post_date_gmt':

$time = current_time('mysql');

wp_update_post(
    array (
        'ID'            => 123, // ID of the post to update
        'post_date'     => $time,
        'post_date_gmt' => get_gmt_from_date( $time )
    )
);

Answer 2

The selected answer is perfect for modifying the "publish date", but in my case I wanted to change the "last modified" date (post_modified and post_modified_gmt in the db). The following is sufficient for that:

wp_update_post( [ 'ID' => $id ] );