Kryptronic Software Support Forum

If you're using realtime shipping via FedEx or UPS, just turn delivery estimates on using settings:

Store / Component / Settings / UPS OnLine Tools Settings
Store / Component / Settings / FedEx Web Services Settings

If you're using some other method, the estimates could be added like with a custom shipping script.  How are you shipping now?

Custom shipping script was the right answer.  Delivery estimates work based on a global array which you can create in your custom shipping script. 

First, turn delivery estimates on for UPS.  That will get those estimates right.  In your UPS script, after the call to the ecom.shiprealtime namespace where you get a result and loop through it, the 'delest' key for each returned rating will hold the delivery estimate.  You can simply append that to your custom shipping option name to display it.  If you use a space and wrap the estimate in parenthesis, it will be stripped where necessary when determining the shipping method name for items in the order.  Example:

// Ensure $custom, $delinfo and $info are defined properly...

$result = $this->include_namespace('ecom','shiprealtime',array('delinfo'  => $delinfo, 'packages' => $info['packages']));

if ((!($this->isError($result))) && (!(empty($result)))) {

     foreach ($result as $num => $service) {

          $custom[$service['name'] . ' (' . $service['delest'] . ')'] = $service['rate'];

     } // End of if statement.

} // End of foreach statement.

For your Royal Mail script, use similar logic.  You won't have a delivery estimate from Royal Mail, but you can figure one out based on delivery times and all you need to do is append that to the shipping method name(s) in your custom script as you see above.  Example:

$now    = $this->globals('core_datetime.epoch');
$custom = array();

$custom['Royal Mail One Day (' .  @date('D, M j',$now + 86400) . ')'] = 9.00;
$custom['Royal Mail OneTwo Day (' .  @date('D, M j',$now + 172800) . ')'] = 7.00;

I hope that helps.