eventespresso / event-espresso-core

     * @return EE_Base_Class           return the EE_Base_Class object so right away you can do something with it

     *                                 (chaining)

     */

    public static function date_time_add(EE_Base_Class $obj, $datetime_field_name, $period = 'years', $value = 1)

    {

        //get the raw UTC date.

        $DateTime = $obj->get_DateTime_object($datetime_field_name);

        $DateTime = EEH_DTT_Helper::calc_date($DateTime, $period, $value);

        return EEH_DTT_Helper::_set_date_time_field($obj, $DateTime, $datetime_field_name);

    }

    /**

     * @param int            $value

     * @return \EE_Base_Class

     */

    public static function date_time_subtract(EE_Base_Class $obj, $datetime_field_name, $period = 'years', $value = 1)

    {

        //get the raw UTC date

        $DateTime = $obj->get_DateTime_object($datetime_field_name);

        $DateTime = EEH_DTT_Helper::calc_date($DateTime, $period, $value, '-');

        return EEH_DTT_Helper::_set_date_time_field($obj, $DateTime, $datetime_field_name);

    }

    /**