diff --git a/copernicusmarine/catalogue_parser/models.py b/copernicusmarine/catalogue_parser/models.py
index fc4dd33e..ad10f1cc 100644
--- a/copernicusmarine/catalogue_parser/models.py
+++ b/copernicusmarine/catalogue_parser/models.py
@@ -100,7 +100,7 @@ class WebApi(Enum):
 
 
 class ServiceNotHandled(Exception):
-    ...
+    pass
 
 
 # service formats
@@ -175,11 +175,11 @@ def _format_admp_valid_start_date(
         if to_timestamp:
             return int(
                 datetime_parser(
-                    arco_data_metadata_producer_valid_start_date.split(".")[0]
+                    arco_data_metadata_producer_valid_start_date
                 ).timestamp()
                 * 1000
             )
-        return arco_data_metadata_producer_valid_start_date.split(".")[0]
+        return arco_data_metadata_producer_valid_start_date
 
     def _convert_elevation_to_depth(self):
         self.coordinates_id = "depth"
@@ -507,11 +507,11 @@ def filter_only_official_versions_and_parts(self):
 
 # Errors
 class DatasetVersionPartNotFound(Exception):
-    ...
+    pass
 
 
 class DatasetVersionNotFound(Exception):
-    ...
+    pass
 
 
 def dataset_version_part_not_found_exception(
diff --git a/copernicusmarine/catalogue_parser/request_structure.py b/copernicusmarine/catalogue_parser/request_structure.py
index 63e98b7c..b28ab788 100644
--- a/copernicusmarine/catalogue_parser/request_structure.py
+++ b/copernicusmarine/catalogue_parser/request_structure.py
@@ -3,10 +3,11 @@
 import pathlib
 import re
 from dataclasses import dataclass, field
-from datetime import datetime
 from json import load
 from typing import Any, Dict, List, Optional
 
+from pendulum import DateTime
+
 from copernicusmarine.core_functions.deprecated_options import (
     DEPRECATED_OPTIONS,
 )
@@ -41,8 +42,8 @@ class DatasetTimeAndSpaceSubset:
     maximum_latitude: Optional[float] = None
     minimum_depth: Optional[float] = None
     maximum_depth: Optional[float] = None
-    start_datetime: Optional[datetime] = None
-    end_datetime: Optional[datetime] = None
+    start_datetime: Optional[DateTime] = None
+    end_datetime: Optional[DateTime] = None
 
 
 @dataclass
@@ -59,8 +60,8 @@ class SubsetRequest:
     minimum_depth: Optional[float] = None
     maximum_depth: Optional[float] = None
     vertical_dimension_as_originally_produced: bool = True
-    start_datetime: Optional[datetime] = None
-    end_datetime: Optional[datetime] = None
+    start_datetime: Optional[DateTime] = None
+    end_datetime: Optional[DateTime] = None
     subset_method: SubsetMethod = DEFAULT_SUBSET_METHOD
     output_filename: Optional[str] = None
     file_format: FileFormat = DEFAULT_FILE_FORMAT
diff --git a/copernicusmarine/command_line_interface/group_subset.py b/copernicusmarine/command_line_interface/group_subset.py
index f53a4d94..267ed421 100644
--- a/copernicusmarine/command_line_interface/group_subset.py
+++ b/copernicusmarine/command_line_interface/group_subset.py
@@ -4,6 +4,7 @@
 from typing import List, Optional
 
 import click
+import pendulum
 
 from copernicusmarine.command_line_interface.exception_handler import (
     log_exception_and_exit,
@@ -400,8 +401,12 @@ def subset(
         minimum_depth,
         maximum_depth,
         vertical_dimension_as_originally_produced,
-        start_datetime,
-        end_datetime,
+        (
+            start_datetime
+            if not start_datetime
+            else pendulum.instance(start_datetime)
+        ),
+        end_datetime if not end_datetime else pendulum.instance(end_datetime),
         subset_method,
         output_filename,
         file_format,
diff --git a/copernicusmarine/core_functions/credentials_utils.py b/copernicusmarine/core_functions/credentials_utils.py
index 2d23304f..9373ac34 100644
--- a/copernicusmarine/core_functions/credentials_utils.py
+++ b/copernicusmarine/core_functions/credentials_utils.py
@@ -36,12 +36,10 @@
 # TODO: handle cache of the credentials without cachier
 
 
-class CredentialCannotBeNone(Exception):
-    ...
+class CredentialCannotBeNone(Exception): ...
 
 
-class InvalidUsernameOrPassword(Exception):
-    ...
+class InvalidUsernameOrPassword(Exception): ...
 
 
 def _load_credential_from_copernicus_marine_configuration_file(
diff --git a/copernicusmarine/core_functions/services_utils.py b/copernicusmarine/core_functions/services_utils.py
index dc0ccb8c..7fbf0cc8 100644
--- a/copernicusmarine/core_functions/services_utils.py
+++ b/copernicusmarine/core_functions/services_utils.py
@@ -181,8 +181,16 @@ def _get_best_arco_service_type(
     time_size = get_size_of_coordinate_subset(
         dataset,
         "time",
-        dataset_subset.start_datetime,
-        dataset_subset.end_datetime,
+        (
+            dataset_subset.start_datetime.in_tz("UTC").naive()
+            if dataset_subset.start_datetime
+            else dataset_subset.start_datetime
+        ),
+        (
+            dataset_subset.end_datetime.in_tz("UTC").naive()
+            if dataset_subset.end_datetime
+            else dataset_subset.end_datetime
+        ),
     )
     dataset_coordinates = dataset.coords
 
@@ -444,7 +452,7 @@ def _get_dataset_start_date_from_service(
 
 
 class ServiceNotAvailable(Exception):
-    ...
+    pass
 
 
 def _warning_dataset_will_be_deprecated(
@@ -498,7 +506,7 @@ def _service_not_available_error(
 
 
 class NoServiceAvailable(Exception):
-    ...
+    pass
 
 
 def _no_service_available_for_command(
diff --git a/copernicusmarine/core_functions/subset.py b/copernicusmarine/core_functions/subset.py
index e325b54f..3da85af4 100644
--- a/copernicusmarine/core_functions/subset.py
+++ b/copernicusmarine/core_functions/subset.py
@@ -1,9 +1,10 @@
 import json
 import logging
 import pathlib
-from datetime import datetime
 from typing import List, Optional
 
+from pendulum import DateTime
+
 from copernicusmarine.catalogue_parser.models import (
     CopernicusMarineDatasetServiceType,
     CopernicusMarineServiceFormat,
@@ -51,8 +52,8 @@ def subset_function(
     minimum_depth: Optional[float],
     maximum_depth: Optional[float],
     vertical_dimension_as_originally_produced: bool,
-    start_datetime: Optional[datetime],
-    end_datetime: Optional[datetime],
+    start_datetime: Optional[DateTime],
+    end_datetime: Optional[DateTime],
     subset_method: SubsetMethod,
     output_filename: Optional[str],
     file_format: FileFormat,
diff --git a/copernicusmarine/core_functions/utils.py b/copernicusmarine/core_functions/utils.py
index 7cc94b08..57a3e70a 100644
--- a/copernicusmarine/core_functions/utils.py
+++ b/copernicusmarine/core_functions/utils.py
@@ -2,7 +2,6 @@
 import logging
 import pathlib
 import re
-from datetime import datetime, timezone
 from importlib.metadata import version
 from typing import (
     Any,
@@ -12,6 +11,7 @@
     Iterable,
     Iterator,
     List,
+    Literal,
     Optional,
     Tuple,
     TypeVar,
@@ -21,7 +21,10 @@
 import cftime
 import numpy
 import pandas as pd
+import pendulum
+import pendulum.exceptions
 import xarray
+from pendulum import DateTime
 from requests import PreparedRequest
 
 from copernicusmarine import __version__ as copernicusmarine_version
@@ -48,11 +51,6 @@
     "%Y-%m-%d %H:%M:%S.%f%Z",
 ]
 
-DATETIME_NON_ISO_FORMATS = [
-    "%Y",
-    "%Y-%m-%dT%H:%M:%S.%fZ",
-]
-
 
 def get_unique_filename(
     filepath: pathlib.Path, overwrite_option: bool
@@ -126,27 +124,44 @@ def construct_query_params_for_marine_data_store_monitoring(
 
 
 class WrongDatetimeFormat(Exception):
-    ...
+    pass
 
 
-def datetime_parser(string: str) -> datetime:
-    if string == "now":
-        return datetime.now(tz=timezone.utc).replace(tzinfo=None)
+def datetime_parser(date: Union[str, numpy.datetime64]) -> DateTime:
+    if date == "now":
+        return pendulum.now(tz="UTC")
     try:
-        parsed_datetime = datetime.fromisoformat(string)
-        if parsed_datetime.tzinfo is None:
-            return parsed_datetime
-        else:
-            return parsed_datetime.astimezone(timezone.utc).replace(
-                tzinfo=None
-            )
-    except ValueError:
-        for datetime_format in DATETIME_NON_ISO_FORMATS:
-            try:
-                return datetime.strptime(string, datetime_format)
-            except ValueError:
-                pass
-    raise WrongDatetimeFormat(string)
+        if isinstance(date, numpy.datetime64):
+            date = str(date)
+        parsed_datetime = pendulum.parse(date)
+        # ignoring types because one needs to pass
+        # `exact=True` to `parse` method to get
+        # something else than `pendulum.DateTime`
+        return parsed_datetime  # type: ignore
+    except pendulum.exceptions.ParserError:
+        pass
+    raise WrongDatetimeFormat(date)
+
+
+def timestamp_parser(
+    timestamp: Union[int, float], unit: Literal["s", "ms"] = "ms"
+) -> DateTime:
+    """
+    Convert a timestamp in milliseconds to a pendulum DateTime object
+    by default. The unit can be changed to seconds by passing "s" as
+    the unit.
+    """
+    conversion_factor = 1 if unit == "s" else 10e3
+    return pendulum.from_timestamp(timestamp / conversion_factor, tz="UTC")
+
+
+def timestamp_or_datestring_to_datetime(
+    date: Union[str, int, numpy.datetime64]
+) -> DateTime:
+    if isinstance(date, int):
+        return timestamp_parser(date)
+    else:
+        return datetime_parser(date)
 
 
 def convert_datetime64_to_netcdf_timestamp(
diff --git a/copernicusmarine/download_functions/download_arco_series.py b/copernicusmarine/download_functions/download_arco_series.py
index 8ecac34e..09de01bf 100644
--- a/copernicusmarine/download_functions/download_arco_series.py
+++ b/copernicusmarine/download_functions/download_arco_series.py
@@ -24,14 +24,12 @@
     LongitudeParameters,
     TemporalParameters,
 )
-from copernicusmarine.download_functions.subset_xarray import (
-    date_to_datetime,
-    subset,
-)
+from copernicusmarine.download_functions.subset_xarray import subset
 from copernicusmarine.download_functions.utils import (
     FileFormat,
     get_filename,
     get_formatted_dataset_size_estimation,
+    timestamp_or_datestring_to_datetime,
 )
 
 logger = logging.getLogger("copernicusmarine")
@@ -153,7 +151,9 @@ def download_zarr(
     )
     start_datetime = subset_request.start_datetime
     if dataset_valid_start_date:
-        minimum_start_date = date_to_datetime(dataset_valid_start_date)
+        minimum_start_date = timestamp_or_datestring_to_datetime(
+            dataset_valid_start_date
+        )
         if (
             not subset_request.start_datetime
             or subset_request.start_datetime < minimum_start_date
diff --git a/copernicusmarine/download_functions/download_original_files.py b/copernicusmarine/download_functions/download_original_files.py
index 1720cc6b..49b3c632 100644
--- a/copernicusmarine/download_functions/download_original_files.py
+++ b/copernicusmarine/download_functions/download_original_files.py
@@ -1,4 +1,3 @@
-import datetime
 import logging
 import os
 import pathlib
@@ -9,8 +8,10 @@
 from typing import Iterator, List, Optional, Tuple
 
 import click
+import pendulum
 from botocore.client import ClientError
 from numpy import append, arange
+from pendulum import DateTime
 from tqdm import tqdm
 
 from copernicusmarine.catalogue_parser.request_structure import (
@@ -28,6 +29,7 @@
     flatten,
     get_unique_filename,
     parse_access_dataset_url,
+    timestamp_parser,
 )
 
 logger = logging.getLogger("copernicusmarine")
@@ -51,7 +53,7 @@ def download_original_files(
     filenames_in_sync_ignored: list[str] = []
     total_size: float = 0.0
     sizes: list[float] = []
-    last_modified_datetimes: list[datetime.datetime] = []
+    last_modified_datetimes: list[DateTime] = []
     filenames_in: list[str] = []
     if get_request.direct_download:
         (
@@ -269,7 +271,7 @@ def _download_header(
         Tuple[str, str],
         list[str],
         List[float],
-        List[datetime.datetime],
+        List[DateTime],
         float,
         list[str],
     ]
@@ -281,7 +283,7 @@ def _download_header(
     filenames: list[str] = []
     sizes: list[float] = []
     total_size = 0.0
-    last_modified_datetimes: list[datetime.datetime] = []
+    last_modified_datetimes: list[DateTime] = []
     etags: list[str] = []
     raw_filenames = _list_files_on_marine_data_lake_s3(
         username, endpoint_url, bucket, path, not only_list_root_path
@@ -290,6 +292,7 @@ def _download_header(
     for filename, size, last_modified_datetime, etag in raw_filenames:
         if not regex or re.search(regex, filename):
             filenames_without_sync.append(filename)
+            last_modified_datetime = pendulum.instance(last_modified_datetime)
             if not sync or _check_needs_to_be_synced(
                 filename, size, last_modified_datetime, directory_out
             ):
@@ -345,7 +348,7 @@ def _download_header_for_direct_download(
     Tuple[str, str],
     List[str],
     List[float],
-    List[datetime.datetime],
+    List[DateTime],
     float,
     list[str],
     list[str],
@@ -410,7 +413,7 @@ def _download_header_for_direct_download(
 def _check_needs_to_be_synced(
     filename: str,
     size: int,
-    last_modified_datetime: datetime.datetime,
+    last_modified_datetime: DateTime,
     directory_out: pathlib.Path,
 ) -> bool:
     filename_out = _local_path_from_s3_url(filename, directory_out)
@@ -421,16 +424,19 @@ def _check_needs_to_be_synced(
         if file_stats.st_size != size:
             return True
         else:
-            last_created_datetime_out = datetime.datetime.fromtimestamp(
-                file_stats.st_ctime, tz=datetime.timezone.utc
+            last_created_datetime_out = timestamp_parser(
+                file_stats.st_mtime, unit="s"
             )
+            # boto3.s3_resource.Object.last_modified is without microsecond
+            # boto3.paginate s3_object["LastModified"] is with microsecond
+            last_modified_datetime = last_modified_datetime.set(microsecond=0)
             return last_modified_datetime > last_created_datetime_out
 
 
 def _create_information_message_before_download(
     filenames: list[str],
     sizes: list[float],
-    last_modified_datetimes: list[datetime.datetime],
+    last_modified_datetimes: list[DateTime],
     total_size: float,
 ) -> str:
     message = "You requested the download of the following files:\n"
@@ -438,13 +444,7 @@ def _create_information_message_before_download(
         filenames[:20], sizes[:20], last_modified_datetimes[:20]
     ):
         message += str(filename)
-        datetime_iso = re.sub(
-            r"\+00:00$",
-            "Z",
-            last_modified_datetime.astimezone(datetime.timezone.utc).isoformat(
-                timespec="seconds"
-            ),
-        )
+        datetime_iso = last_modified_datetime.in_tz("UTC").to_iso8601_string()
         message += f" - {format_file_size(float(size))} - {datetime_iso}\n"
     if len(filenames) > 20:
         message += f"Printed 20 out of {len(filenames)} files\n"
@@ -466,7 +466,7 @@ def _list_files_on_marine_data_lake_s3(
     bucket: str,
     prefix: str,
     recursive: bool,
-) -> list[tuple[str, int, datetime.datetime, str]]:
+) -> list[tuple[str, int, DateTime, str]]:
 
     s3_client, _ = get_configured_boto3_session(
         endpoint_url, ["ListObjects"], username
@@ -483,7 +483,7 @@ def _list_files_on_marine_data_lake_s3(
         *map(lambda page: page.get("Contents", []), page_iterator)
     )
 
-    files_already_found: list[tuple[str, int, datetime.datetime, str]] = []
+    files_already_found: list[tuple[str, int, DateTime, str]] = []
     for s3_object in s3_objects:
         files_already_found.append(
             (
@@ -498,7 +498,7 @@ def _list_files_on_marine_data_lake_s3(
 
 def _get_file_size_and_last_modified(
     endpoint_url: str, bucket: str, file_in: str, username: str
-) -> Optional[Tuple[int, datetime.datetime]]:
+) -> Optional[Tuple[int, DateTime]]:
     s3_client, _ = get_configured_boto3_session(
         endpoint_url, ["HeadObject"], username
     )
@@ -508,7 +508,9 @@ def _get_file_size_and_last_modified(
             Bucket=bucket,
             Key=file_in.replace(f"s3://{bucket}/", ""),
         )
-        return s3_object["ContentLength"], s3_object["LastModified"]
+        return s3_object["ContentLength"], pendulum.instance(
+            s3_object["LastModified"]
+        )
     except ClientError as e:
         if "404" in str(e):
             logger.warning(
diff --git a/copernicusmarine/download_functions/subset_parameters.py b/copernicusmarine/download_functions/subset_parameters.py
index 343e81a8..65128c71 100644
--- a/copernicusmarine/download_functions/subset_parameters.py
+++ b/copernicusmarine/download_functions/subset_parameters.py
@@ -1,7 +1,8 @@
 from dataclasses import dataclass, field
-from datetime import datetime
 from typing import Optional
 
+from pendulum import DateTime
+
 
 @dataclass
 class LatitudeParameters:
@@ -27,8 +28,8 @@ class GeographicalParameters:
 
 @dataclass
 class TemporalParameters:
-    start_datetime: Optional[datetime] = None
-    end_datetime: Optional[datetime] = None
+    start_datetime: Optional[DateTime] = None
+    end_datetime: Optional[DateTime] = None
 
 
 @dataclass
diff --git a/copernicusmarine/download_functions/subset_xarray.py b/copernicusmarine/download_functions/subset_xarray.py
index 39d9afb3..97a13c91 100644
--- a/copernicusmarine/download_functions/subset_xarray.py
+++ b/copernicusmarine/download_functions/subset_xarray.py
@@ -1,12 +1,11 @@
 import logging
 import typing
-from datetime import datetime
 from decimal import Decimal
 from typing import List, Literal, Optional, Union
 
 import numpy
 import xarray
-from pandas import Timestamp
+from pendulum import DateTime
 
 from copernicusmarine.catalogue_parser.models import (
     CopernicusMarineDatasetServiceType,
@@ -21,7 +20,10 @@
     VariableDoesNotExistInTheDataset,
 )
 from copernicusmarine.core_functions.models import SubsetMethod
-from copernicusmarine.core_functions.utils import ServiceNotSupported
+from copernicusmarine.core_functions.utils import (
+    ServiceNotSupported,
+    timestamp_or_datestring_to_datetime,
+)
 from copernicusmarine.download_functions.subset_parameters import (
     DepthParameters,
     GeographicalParameters,
@@ -71,7 +73,7 @@
 def _dataset_custom_sel(
     dataset: xarray.Dataset,
     coord_type: Literal["latitude", "longitude", "depth", "time"],
-    coord_selection: Union[float, slice, datetime, None],
+    coord_selection: Union[float, slice, DateTime, None],
     method: Union[str, None] = None,
 ) -> xarray.Dataset:
     for coord_label in COORDINATES_LABEL[coord_type]:
@@ -105,8 +107,8 @@ def _dataset_custom_sel(
 def get_size_of_coordinate_subset(
     dataset: xarray.Dataset,
     coordinate: str,
-    minimum: Optional[Union[float, datetime]],
-    maximum: Optional[Union[float, datetime]],
+    minimum: Optional[Union[float, DateTime]],
+    maximum: Optional[Union[float, DateTime]],
 ) -> int:
     for label in COORDINATES_LABEL[coordinate]:
         if label in dataset.sizes:
@@ -220,8 +222,16 @@ def _temporal_subset(
     dataset: xarray.Dataset,
     temporal_parameters: TemporalParameters,
 ) -> xarray.Dataset:
-    start_datetime = temporal_parameters.start_datetime
-    end_datetime = temporal_parameters.end_datetime
+    start_datetime = (
+        temporal_parameters.start_datetime.in_tz("UTC").naive()
+        if temporal_parameters.start_datetime
+        else temporal_parameters.start_datetime
+    )
+    end_datetime = (
+        temporal_parameters.end_datetime.in_tz("UTC").naive()
+        if temporal_parameters.end_datetime
+        else temporal_parameters.end_datetime
+    )
     if start_datetime is not None or end_datetime is not None:
         temporal_selection = (
             start_datetime
@@ -490,8 +500,12 @@ def check_dataset_subset_bounds(
                 times_min = dataset_valid_date
             else:
                 times_min = times.min()
-            dataset_minimum_coordinate_value = date_to_datetime(times_min)
-            dataset_maximum_coordinate_value = date_to_datetime(times.max())
+            dataset_minimum_coordinate_value = (
+                timestamp_or_datestring_to_datetime(times_min)
+            )
+            dataset_maximum_coordinate_value = (
+                timestamp_or_datestring_to_datetime(times.max())
+            )
             user_minimum_coordinate_value = (
                 dataset_subset.start_datetime
                 if dataset_subset.start_datetime is not None
@@ -531,20 +545,13 @@ def check_dataset_subset_bounds(
             )
 
 
-def date_to_datetime(date: Union[str, int]) -> datetime:
-    if isinstance(date, int):
-        return Timestamp(date * 1e6).to_pydatetime()
-    else:
-        return Timestamp(date).to_pydatetime().replace(tzinfo=None)
-
-
 @typing.no_type_check
 def _check_coordinate_overlap(
     dimension: str,
-    user_minimum_coordinate_value: Union[float, datetime],
-    user_maximum_coordinate_value: Union[float, datetime],
-    dataset_minimum_coordinate_value: Union[float, datetime],
-    dataset_maximum_coordinate_value: Union[float, datetime],
+    user_minimum_coordinate_value: Union[float, DateTime],
+    user_maximum_coordinate_value: Union[float, DateTime],
+    dataset_minimum_coordinate_value: Union[float, DateTime],
+    dataset_maximum_coordinate_value: Union[float, DateTime],
     is_strict: bool,
 ) -> None:
     message = (
diff --git a/copernicusmarine/download_functions/utils.py b/copernicusmarine/download_functions/utils.py
index 762377e8..e6514fb9 100644
--- a/copernicusmarine/download_functions/utils.py
+++ b/copernicusmarine/download_functions/utils.py
@@ -1,15 +1,17 @@
 import logging
-from datetime import datetime
 from pathlib import Path
 from typing import Optional
 
 import xarray
-from pandas import Timestamp
+from pendulum import DateTime
 
 from copernicusmarine.core_functions.models import (
     DEFAULT_FILE_EXTENSIONS,
     FileFormat,
 )
+from copernicusmarine.core_functions.utils import (
+    timestamp_or_datestring_to_datetime,
+)
 from copernicusmarine.download_functions.subset_xarray import COORDINATES_LABEL
 
 logger = logging.getLogger("copernicusmarine")
@@ -63,15 +65,14 @@ def _build_filename_from_dataset(
 
     min_time_coordinate = _get_min_coordinate(dataset, "time")
     max_time_coordinate = _get_max_coordinate(dataset, "time")
-
     datetimes = _format_datetimes(
         (
-            Timestamp(min_time_coordinate).to_pydatetime()
+            timestamp_or_datestring_to_datetime(min_time_coordinate)
             if min_time_coordinate is not None
             else None
         ),
         (
-            Timestamp(max_time_coordinate).to_pydatetime()
+            timestamp_or_datestring_to_datetime(max_time_coordinate)
             if max_time_coordinate is not None
             else None
         ),
@@ -154,17 +155,17 @@ def _format_depths(
 
 
 def _format_datetimes(
-    minimum_datetime: Optional[datetime], maximum_datetime: Optional[datetime]
+    minimum_datetime: Optional[DateTime], maximum_datetime: Optional[DateTime]
 ) -> str:
     if minimum_datetime is None or maximum_datetime is None:
         return ""
     else:
         if minimum_datetime == maximum_datetime:
-            formatted_datetime = f"{minimum_datetime.strftime('%Y-%m-%d')}"
+            formatted_datetime = f"{minimum_datetime.format('YYYY-MM-DD')}"
         else:
             formatted_datetime = (
-                f"{minimum_datetime.strftime('%Y-%m-%d')}-"
-                f"{maximum_datetime.strftime('%Y-%m-%d')}"
+                f"{minimum_datetime.format('YYYY-MM-DD')}-"
+                f"{maximum_datetime.format('YYYY-MM-DD')}"
             )
         return formatted_datetime
 
diff --git a/copernicusmarine/python_interface/load_utils.py b/copernicusmarine/python_interface/load_utils.py
index 34a1837e..16a66f3b 100644
--- a/copernicusmarine/python_interface/load_utils.py
+++ b/copernicusmarine/python_interface/load_utils.py
@@ -18,7 +18,7 @@
 from copernicusmarine.core_functions.utils import ServiceNotSupported
 from copernicusmarine.download_functions.subset_xarray import (
     check_dataset_subset_bounds,
-    date_to_datetime,
+    timestamp_or_datestring_to_datetime,
 )
 
 
@@ -56,7 +56,7 @@ def load_data_object_from_load_request(
         CopernicusMarineDatasetServiceType.STATIC_ARCO,
     ]:
         if retrieval_service.dataset_valid_start_date:
-            parsed_start_datetime = date_to_datetime(
+            parsed_start_datetime = timestamp_or_datestring_to_datetime(
                 retrieval_service.dataset_valid_start_date
             )
             if (
diff --git a/copernicusmarine/python_interface/utils.py b/copernicusmarine/python_interface/utils.py
index ab549b87..697b9cab 100644
--- a/copernicusmarine/python_interface/utils.py
+++ b/copernicusmarine/python_interface/utils.py
@@ -1,12 +1,17 @@
 from datetime import datetime
 from typing import Optional, Union
 
+import pendulum
+from pendulum import DateTime
+
 from copernicusmarine.core_functions.utils import datetime_parser
 
 
 def homogenize_datetime(
     input_datetime: Optional[Union[datetime, str]]
-) -> Optional[datetime]:
+) -> Optional[DateTime]:
+    if input_datetime is None:
+        return None
     if isinstance(input_datetime, str):
         return datetime_parser(input_datetime)
-    return input_datetime
+    return pendulum.instance(input_datetime)
diff --git a/poetry.lock b/poetry.lock
index 0cd3c121..5dc173d7 100644
--- a/poetry.lock
+++ b/poetry.lock
@@ -1,4 +1,4 @@
-# This file is automatically @generated by Poetry 1.8.2 and should not be changed by hand.
+# This file is automatically @generated by Poetry 1.6.1 and should not be changed by hand.
 
 [[package]]
 name = "aiohttp"
@@ -1298,6 +1298,105 @@ toolz = "*"
 [package.extras]
 complete = ["blosc", "numpy (>=1.20.0)", "pandas (>=1.3)", "pyzmq"]
 
+[[package]]
+name = "pendulum"
+version = "3.0.0"
+description = "Python datetimes made easy"
+optional = false
+python-versions = ">=3.8"
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+]
+
+[package.dependencies]
+python-dateutil = ">=2.6"
+tzdata = ">=2020.1"
+
+[package.extras]
+test = ["time-machine (>=2.6.0)"]
+
 [[package]]
 name = "pexpect"
 version = "4.9.0"
@@ -1907,4 +2006,4 @@ test = ["big-O", "importlib-resources", "jaraco.functools", "jaraco.itertools",
 [metadata]
 lock-version = "2.0"
 python-versions = ">=3.9,<3.13"
-content-hash = "10f7e27b97411bfe5cf27642ad7b4ae7c5a65b0634daa48c1551eb67dbe941f4"
+content-hash = "2248793fb390933099ce694951481e01fc3bacfb49ec217e037ae5f43b29d715"
diff --git a/pyproject.toml b/pyproject.toml
index eae54043..f26d0ba4 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -24,6 +24,7 @@ nest-asyncio = ">=1.5.8"
 pystac = ">=1.8.3"
 lxml = ">=4.9.0"
 numpy = ">=1.23.0,<2.0.0"
+pendulum = "^3.0.0"
 
 [tool.poetry.dev-dependencies]
 pre-commit = "^2.20.0"
diff --git a/tests/test_utility_functions.py b/tests/test_utility_functions.py
index 6f867292..f975d37c 100644
--- a/tests/test_utility_functions.py
+++ b/tests/test_utility_functions.py
@@ -1,4 +1,4 @@
-from datetime import datetime
+from datetime import datetime, timezone
 
 from freezegun import freeze_time
 
@@ -9,23 +9,29 @@ class TestUtilityFunctions:
     @freeze_time("2012-01-14 03:21:34", tz_offset=-2)
     def test_datetime_parser(self):
         # all parsed dates are in UTC
-        assert datetime_parser("now") == datetime(2012, 1, 14, 1, 21, 34)
+        assert datetime_parser("now") == datetime(
+            2012, 1, 14, 1, 21, 34, tzinfo=timezone.utc
+        )
         assert datetime_parser("2012-01-14T03:21:34.000000+02:00") == datetime(
-            2012, 1, 14, 1, 21, 34
+            2012, 1, 14, 1, 21, 34, tzinfo=timezone.utc
         )
 
         # All format are supported
-        assert datetime_parser("2012") == datetime(2012, 1, 1, 0, 0, 0)
-        assert datetime_parser("2012-01-14") == datetime(2012, 1, 14, 0, 0, 0)
+        assert datetime_parser("2012") == datetime(
+            2012, 1, 1, 0, 0, 0, tzinfo=timezone.utc
+        )
+        assert datetime_parser("2012-01-14") == datetime(
+            2012, 1, 14, 0, 0, 0, tzinfo=timezone.utc
+        )
         assert datetime_parser("2012-01-14T03:21:34") == datetime(
-            2012, 1, 14, 3, 21, 34
+            2012, 1, 14, 3, 21, 34, tzinfo=timezone.utc
         )
         assert datetime_parser("2012-01-14 03:21:34") == datetime(
-            2012, 1, 14, 3, 21, 34
+            2012, 1, 14, 3, 21, 34, tzinfo=timezone.utc
         )
         assert datetime_parser("2012-01-14T03:21:34.000000") == datetime(
-            2012, 1, 14, 3, 21, 34
+            2012, 1, 14, 3, 21, 34, tzinfo=timezone.utc
         )
         assert datetime_parser("2012-01-14T03:21:34.000000Z") == datetime(
-            2012, 1, 14, 3, 21, 34
+            2012, 1, 14, 3, 21, 34, tzinfo=timezone.utc
         )