diff --git a/mlair/data_handler/data_handler_wrf_chem.py b/mlair/data_handler/data_handler_wrf_chem.py
index df1e958d6acb7b0b5d5801f99a7077a3ab0a9a13..36fbb0c7e473eb2fddbc7253c3344eda7e112e6a 100644
--- a/mlair/data_handler/data_handler_wrf_chem.py
+++ b/mlair/data_handler/data_handler_wrf_chem.py
@@ -66,6 +66,7 @@ class BaseWrfChemDataLoader:
                  staged_rotation_opts: Dict = DEFAULT_STAGED_ROTATION_opts,
                  vars_to_rotate: Tuple[Tuple[Tuple[str, str], Tuple[str, str]]] = DEFAULT_VARS_TO_ROTATE,
                  staged_dimension_mapping=None, stag_ending='_stag',
+                 date_format_of_nc_file=None,
 
                  ):
         # super().__init__()
@@ -89,6 +90,9 @@ class BaseWrfChemDataLoader:
 
         self.start_time = start_time
         self.end_time = end_time
+        if date_format_of_nc_file is None:
+            date_format_of_nc_file = "%Y-%m-%d"
+        self.date_format_of_nc_file = date_format_of_nc_file
 
         # if rechunk_values is None:
         #     self.rechunk_values = {self.time_dim_name: 1}
@@ -128,14 +132,14 @@ class BaseWrfChemDataLoader:
         if (self.start_time is None) and (self.end_time is None):
             return os.path.join(self.data_path, self.common_file_starter + '*')
         elif (self.start_time is not None) and (self.end_time is not None):
-            path_list = []
+            path_list = set()
             for day in pd.date_range(self.start_time, self.end_time):
-                path_list += sorted(glob.glob(os.path.join(self.data_path,
-                                                           self.common_file_starter) + '*' + day.strftime(
-                    "%Y-%m-%d") + '*'
-                                              ))
+                path_list.add(sorted(glob.glob(os.path.join(self.data_path,
+                                                            self.common_file_starter) + '*' + day.strftime(
+                    self.date_format_of_nc_file) + '*'
+                                               ))[0])
 
-            return path_list
+            return list(path_list)
         else:
             raise ValueError(f"`start_time' and `end_time' must both be given or None.")
 
@@ -150,7 +154,7 @@ class BaseWrfChemDataLoader:
                                      parallel=True, decode_cf=False)
         else:
             data = xr.open_mfdataset(paths=self.dataset_search_str, combine='nested', concat_dim=self.time_dim_name,
-                                     parallel=True, decode_cf=False, preprocess=self.preprocess_fkt_for_loader)
+                                     parallel=True, decode_cf=False, preprocess=self.preprocess_fkt_for_loader, )
         data = xr.decode_cf(data)
         # if self.variables is not None:
         #     data = self.preprocess_fkt_for_loader(data)
@@ -447,7 +451,9 @@ class DataHandlerSingleGridColumn(DataHandlerSingleStation):
     def __init__(self, *args, external_coords_file=None,
                  var_logical_z_coord_selector=None,
                  targetvar_logical_z_coord_selector=None,
-                 rechunk_values=None, **kwargs):
+                 rechunk_values=None,
+                 date_format_of_nc_file=None,
+                 **kwargs):
         self.external_coords_file = external_coords_file
         self.var_logical_z_coord_selector = self._ret_z_coord_select_if_valid(var_logical_z_coord_selector,
                                                                               as_input=True)
@@ -458,6 +464,7 @@ class DataHandlerSingleGridColumn(DataHandlerSingleStation):
                                                                              self.targetvar_logical_z_coord_selector)
         self.__loader = None
         self.rechunk_values = rechunk_values
+        self.date_format_of_nc_file = date_format_of_nc_file
         super().__init__(*args, **kwargs)
 
     @staticmethod
@@ -513,6 +520,7 @@ class DataHandlerSingleGridColumn(DataHandlerSingleStation):
                                                    z_coord_selector=self._joint_z_coord_selector,
                                                    start_time=self.start,
                                                    end_time=self.end,
+                                                   date_format_of_nc_file=self.date_format_of_nc_file
                                                    )
         self.__loader = loader