OK, got it. I put together a quick form that shows how this can work. You can download the form here:
[SITE REMOVED]
Save that to your desktop, then go to Forms > Import/Export > Import Forms on your site. Before you can use the form, you need this code to populate three fields in the form with the dates:
add_filter( 'gform_field_value', 'all_the_dates', 10, 3 );
function all_the_dates( $value, $field, $name ) {
// "21st of June" is the format we want
$local_timestamp = GFCommon::get_local_timestamp( time() );
$three_timestamp = ( 86400 * 3 ) + $local_timestamp;
$seven_timestamp = ( 86400 * 7 ) + $local_timestamp;
$today = date_i18n( 'jS \of F', $local_timestamp, true );
$three = date_i18n( 'jS \of F', $three_timestamp, true );
$seven = date_i18n( 'jS \of F', $seven_timestamp, true );
$values = array(
'todays_date' => $today,
'three_days' => $three,
'seven_days' => $seven,
);
return isset( $values[ $name ] ) ? $values[ $name ] : $value;
}
That is PHP code to go into your theme functions.php file, or a custom functionality plugin if you are using one.
Now, with that code on your site, preview the form you imported. You will see the three date fields pre-populated by the code (screenshot). If you submit, you will see on the confirmation screen the estimated delivery dates (screenshot).
The three date field strings are visible now, but you can make those fields hidden visibility if you like, and the procedure will still work.
Let me know if you have any questions.