diff --git a/erddapy/core/url.py b/erddapy/core/url.py
index 5844941..8f31390 100644
--- a/erddapy/core/url.py
+++ b/erddapy/core/url.py
@@ -3,17 +3,13 @@
 from __future__ import annotations
 
 import copy
+import datetime
 import functools
 import io
 from collections import OrderedDict
-from typing import TYPE_CHECKING
-
-if TYPE_CHECKING:
-    from datetime import datetime
 from typing import BinaryIO
 from urllib import parse
 
-import pytz
 import requests
 from pandas import to_datetime
 
@@ -201,7 +197,7 @@ def _is_quoted(url: str) -> bool:
 
 
 def parse_dates(
-    date_time: datetime | str,
+    date_time: datetime.datetime | str,
     *,
     dayfirst: OptionalBool = False,
     yearfirst: OptionalBool = False,
@@ -222,10 +218,11 @@ def parse_dates(
     else:
         parse_date_time = date_time
 
+    # Naive datetimes tzinfo must be replaced, tz-aware should be converted.
     if not parse_date_time.tzinfo:
-        parse_date_time = pytz.utc.localize(parse_date_time)
+        parse_date_time = parse_date_time.replace(tzinfo=datetime.UTC)
     else:
-        parse_date_time = parse_date_time.astimezone(pytz.utc)
+        parse_date_time = parse_date_time.astimezone(datetime.UTC)
 
     return parse_date_time.timestamp()
 
@@ -306,7 +303,7 @@ def get_search_url(  # noqa: PLR0913
         search_for = parse.quote_plus(search_for)
         base += "&searchFor={searchFor}"
 
-    # Convert dates from datetime to `seconds since 1970-01-01T00:00:00Z`.
+    # Convert dates from datetime.datetime to secs since 1970-01-01T00:00:00Z.
     min_time = kwargs.pop("min_time", "")
     max_time = kwargs.pop("max_time", "")
     if min_time and not _check_substrings(min_time):
diff --git a/requirements-dev.txt b/requirements-dev.txt
index 878bc49..7c10a6c 100644
--- a/requirements-dev.txt
+++ b/requirements-dev.txt
@@ -11,7 +11,6 @@ nbsphinx
 netcdf4
 pendulum>=2.0.1
 pooch
-pre-commit
 pytest
 pytest-cov
 pytest-recording
@@ -21,7 +20,6 @@ scitools-iris>=3.3.0
 setuptools_scm
 sphinx
 twine
-types-pytz
 types-requests
 wheel
 xarray
diff --git a/requirements.txt b/requirements.txt
index 9d4ecba..cd9273f 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,3 +1,2 @@
 pandas>=0.25.2,<4
-pytz
 requests
diff --git a/tests/test_erddapy.py b/tests/test_erddapy.py
index 1f285fb..1a39a5c 100644
--- a/tests/test_erddapy.py
+++ b/tests/test_erddapy.py
@@ -1,11 +1,11 @@
 """Test ERDDAP functionality."""
 
+from __future__ import annotations
+
 import datetime
-import sys
+from zoneinfo import ZoneInfo
 
-import packaging.version
 import pytest
-import pytz
 
 from erddapy.core.griddap import (
     _griddap_check_constraints,
@@ -17,23 +17,16 @@
     parse_dates,
 )
 
-if packaging.version.parse(
-    f"{sys.version_info.major}.{sys.version_info.minor}",
-) < packaging.version.parse(
-    "3.11",
-):
-    datetime.UTC = datetime.timezone.utc
-
 
 def test_parse_dates_utc_datetime():
     """UTC timestamp at 1970-1-1 must be 0."""
-    d = datetime.datetime(1970, 1, 1, 0, 0, tzinfo=pytz.utc)
+    d = datetime.datetime(1970, 1, 1, 0, 0, tzinfo=datetime.UTC)
     assert parse_dates(d) == 0
 
 
 def test_parse_dates_nonutc_datetime():
     """Non-UTC timestamp at 1970-1-1 must have the zone offset."""
-    d = datetime.datetime(1970, 1, 1, tzinfo=pytz.timezone("US/Eastern"))
+    d = datetime.datetime(1970, 1, 1, tzinfo=ZoneInfo("US/Eastern"))
     assert parse_dates(d) == abs(d.utcoffset().total_seconds())