|  | @@ 289-295 (lines=7) @@ | 
                                                            
                                    | 286 |  |      * @throws EE_Error | 
                                                            
                                    | 287 |  |      * @throws Exception | 
                                                            
                                    | 288 |  |      */ | 
                                                            
                                    | 289 |  |     public static function date_time_add(EE_Base_Class $obj, $datetime_field_name, $period = 'years', $value = 1) | 
                                                            
                                    | 290 |  |     { | 
                                                            
                                    | 291 |  |         //get the raw UTC date. | 
                                                            
                                    | 292 |  |         $DateTime = $obj->get_DateTime_object($datetime_field_name); | 
                                                            
                                    | 293 |  |         $DateTime = EEH_DTT_Helper::calc_date($DateTime, $period, $value); | 
                                                            
                                    | 294 |  |         return EEH_DTT_Helper::_set_date_time_field($obj, $DateTime, $datetime_field_name); | 
                                                            
                                    | 295 |  |     } | 
                                                            
                                    | 296 |  |  | 
                                                            
                                    | 297 |  |  | 
                                                            
                                    | 298 |  |     /** | 
                                                                                
                                |  | @@ 310-316 (lines=7) @@ | 
                                                            
                                    | 307 |  |      * @throws EE_Error | 
                                                            
                                    | 308 |  |      * @throws Exception | 
                                                            
                                    | 309 |  |      */ | 
                                                            
                                    | 310 |  |     public static function date_time_subtract(EE_Base_Class $obj, $datetime_field_name, $period = 'years', $value = 1) | 
                                                            
                                    | 311 |  |     { | 
                                                            
                                    | 312 |  |         //get the raw UTC date | 
                                                            
                                    | 313 |  |         $DateTime = $obj->get_DateTime_object($datetime_field_name); | 
                                                            
                                    | 314 |  |         $DateTime = EEH_DTT_Helper::calc_date($DateTime, $period, $value, '-'); | 
                                                            
                                    | 315 |  |         return EEH_DTT_Helper::_set_date_time_field($obj, $DateTime, $datetime_field_name); | 
                                                            
                                    | 316 |  |     } | 
                                                            
                                    | 317 |  |  | 
                                                            
                                    | 318 |  |  | 
                                                            
                                    | 319 |  |     /** |