How to do Early Bird pricing

See the discount examples for this.
In your case, for example for event with id 5:

add_action('eme_insert_rsvp_action', 'my_eme_discount_function',20,1);
function my_eme_discount_function($booking) {
   global $wpdb;
   $bookings_table = $wpdb->prefix.BOOKINGS_TBNAME;
   $where = array();
   $fields = array();

   $booking_id = $booking['booking_id'];
   $event_id = $booking['event_id'];

   if ($event_id == 5) {        /* put in the event_id that needs processing, or leave out this line to process all events */
      $seats=$booking['booking_seats'];
      $price=$booking['booking_price'];

      // check the booking date
      if ($booking['creation_date datetime']) < "....") {
         $price = xxxx;
      }

      $fields['booking_price'] = $price;
      $where['booking_id'] = $booking['booking_id'];
      $wpdb->update($bookings_table, $fields, $where);
   }
   return;
}

Change

if ($booking['creation_date datetime']) < "....") {
         $price = xxxx;
      }

to your liking (and the event-id too). Or get all event details with:
eme_get_event($event_id);
and compare the booking creation date/time with $event[‘event_start_date’] and $event[‘event_start_time’]