Gravity Forms // gform_pre_submission filter based on field CSS class

hjs-gform-pre-submission-css-class.php

<?php 
add_action( 'gform_pre_submission', 'pre_submission_handler_one' );
function pre_submission_handler_one( $form ) {
	foreach ( $form['fields'] as $field ) {
        $cssClass = $field->cssClass;
        if ( strpos($cssClass, 'test') !== false) {
            $field_id = $field->id;
            $date = new DateTime( 'now' );
            $_POST["input_$field_id"] = $date->format('U');
        }
    }
}