diff --git a/pykeepass/baseelement.py b/pykeepass/baseelement.py
index 4a5230e6..2ca238fa 100644
--- a/pykeepass/baseelement.py
+++ b/pykeepass/baseelement.py
@@ -2,7 +2,7 @@
 import uuid
 from lxml import etree
 from lxml.builder import E
-from datetime import datetime
+from datetime import datetime, timezone
 
 
 class BaseElement():
@@ -17,9 +17,9 @@ def __init__(self, element, kp=None, icon=None, expires=False,
         )
         if icon:
             self._element.append(E.IconID(icon))
-        current_time_str = self._kp._encode_time(datetime.now())
+        current_time_str = self._kp._encode_time(datetime.now(timezone.utc))
         if expiry_time:
-            expiry_time_str = self._kp._encode_time(expiry_time)
+            expiry_time_str = self._kp._encode_time(expiry_time.astimezone(timezone.utc))
         else:
             expiry_time_str = current_time_str
 
@@ -116,8 +116,8 @@ def expires(self, value):
     def expired(self):
         if self.expires:
             return (
-                self._kp._datetime_to_utc(datetime.utcnow()) >
-                self._kp._datetime_to_utc(self.expiry_time)
+                datetime.now(timezone.utc) >
+                self.expiry_time
             )
 
         return False
@@ -178,7 +178,7 @@ def touch(self, modify=False):
         Args:
             modify (bool): update access time as well a modification time
         """
-        now = datetime.now()
+        now = datetime.now(timezone.utc)
         self.atime = now
         if modify:
             self.mtime = now
diff --git a/pykeepass/pykeepass.py b/pykeepass/pykeepass.py
index 761828b4..93eb71e9 100644
--- a/pykeepass/pykeepass.py
+++ b/pykeepass/pykeepass.py
@@ -10,8 +10,7 @@
 
 from binascii import Error as BinasciiError
 from construct import Container, ChecksumError, CheckError
-from dateutil import parser, tz
-from datetime import datetime, timedelta
+from datetime import datetime, timedelta, timezone
 from lxml import etree
 from lxml.builder import E
 from pathlib import Path
@@ -29,7 +28,7 @@
 BLANK_DATABASE_FILENAME = "blank_database.kdbx"
 BLANK_DATABASE_LOCATION = os.path.join(os.path.dirname(os.path.realpath(__file__)), BLANK_DATABASE_FILENAME)
 BLANK_DATABASE_PASSWORD = "password"
-
+DT_ISOFORMAT = "%Y-%m-%dT%H:%M:%S%fZ"
 
 class PyKeePass():
     """Open a KeePass database
@@ -707,7 +706,7 @@ def password(self):
     @password.setter
     def password(self, password):
         self._password = password
-        self.credchange_date = datetime.now()
+        self.credchange_date = datetime.now(timezone.utc)
 
     @property
     def keyfile(self):
@@ -717,7 +716,7 @@ def keyfile(self):
     @keyfile.setter
     def keyfile(self, keyfile):
         self._keyfile = keyfile
-        self.credchange_date = datetime.now()
+        self.credchange_date = datetime.now(timezone.utc)
 
     @property
     def credchange_required_days(self):
@@ -754,8 +753,8 @@ def credchange_date(self):
 
     @credchange_date.setter
     def credchange_date(self, date):
-        time = self._xpath('/KeePassFile/Meta/MasterKeyChanged', first=True)
-        time.text = self._encode_time(date)
+        mk_time = self._xpath('/KeePassFile/Meta/MasterKeyChanged', first=True)
+        mk_time.text = self._encode_time(date)
 
     @property
     def credchange_required(self):
@@ -763,7 +762,7 @@ def credchange_required(self):
         change_date = self.credchange_date
         if change_date is None or self.credchange_required_days == -1:
             return False
-        now_date = self._datetime_to_utc(datetime.now())
+        now_date = datetime.now(timezone.utc)
         return (now_date - change_date).days > self.credchange_required_days
 
     @property
@@ -772,30 +771,23 @@ def credchange_recommended(self):
         change_date = self.credchange_date
         if change_date is None or self.credchange_recommended_days == -1:
             return False
-        now_date = self._datetime_to_utc(datetime.now())
+        now_date = datetime.now(timezone.utc)
         return (now_date - change_date).days > self.credchange_recommended_days
 
     # ---------- Datetime Functions ----------
 
-    def _datetime_to_utc(self, dt):
-        """Convert naive datetimes to UTC"""
-
-        if not dt.tzinfo:
-            dt = dt.replace(tzinfo=tz.gettz())
-        return dt.astimezone(tz.gettz('UTC'))
-
     def _encode_time(self, value):
         """bytestring or plaintext string: Convert datetime to base64 or plaintext string"""
 
         if self.version >= (4, 0):
             diff_seconds = int(
                 (
-                    self._datetime_to_utc(value) -
+                    value -
                     datetime(
                         year=1,
                         month=1,
                         day=1,
-                        tzinfo=tz.gettz('UTC')
+                        tzinfo=timezone.utc
                     )
                 ).total_seconds()
             )
@@ -803,7 +795,7 @@ def _encode_time(self, value):
                 struct.pack('<Q', diff_seconds)
             ).decode('utf-8')
         else:
-            return self._datetime_to_utc(value).isoformat()
+            return value.strftime(DT_ISOFORMAT)
 
     def _decode_time(self, text):
         """datetime.datetime: Convert base64 time or plaintext time to datetime"""
@@ -812,21 +804,15 @@ def _decode_time(self, text):
             # decode KDBX4 date from b64 format
             try:
                 return (
-                    datetime(year=1, month=1, day=1, tzinfo=tz.gettz('UTC')) +
+                    datetime(year=1, month=1, day=1, tzinfo=timezone.utc) +
                     timedelta(
                         seconds=struct.unpack('<Q', base64.b64decode(text))[0]
                     )
                 )
             except BinasciiError:
-                return parser.parse(
-                    text,
-                    tzinfos={'UTC': tz.gettz('UTC')}
-                )
+                return datetime.strptime(text, DT_ISOFORMAT).replace(tzinfo=timezone.utc)
         else:
-            return parser.parse(
-                text,
-                tzinfos={'UTC': tz.gettz('UTC')}
-            )
+            return datetime.strptime(text, DT_ISOFORMAT).replace(tzinfo=timezone.utc)
 
 def create_database(
         filename, password=None, keyfile=None, transformed_key=None
diff --git a/pykeepass/version.py b/pykeepass/version.py
index 6ca1dadc..c408a4e9 100644
--- a/pykeepass/version.py
+++ b/pykeepass/version.py
@@ -1,3 +1,5 @@
-__version__ = "4.0.6"
-
 __all__= ["__version__"]
+
+# FIXME: switch to using importlib.metadata when dropping Python<=3.7
+import pkg_resources
+__version__ = pkg_resources.get_distribution('pykeepass').version
diff --git a/pyproject.toml b/pyproject.toml
index 33b4e51b..61e103d3 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,5 +1,6 @@
 [project]
 name = "pykeepass"
+version = "4.0.7"
 readme = "README.rst"
 description = "Python library to interact with keepass databases (supports KDBX3 and KDBX4)"
 authors = [
@@ -9,7 +10,6 @@ authors = [
 license = {text = "GPL-3.0"}
 keywords = ["vault", "keepass"]
 dependencies = [
-    "python-dateutil>=2.7.0",
     "construct>=2.10.53",
     "argon2_cffi>=18.1.0",
     "pycryptodomex>=3.6.2",
diff --git a/setup.py b/setup.py
deleted file mode 100644
index b8d13a3c..00000000
--- a/setup.py
+++ /dev/null
@@ -1,30 +0,0 @@
-from setuptools import find_packages, setup
-
-with open("README.rst") as file:
-    README = file.read()
-
-version = {}
-with open("pykeepass/version.py") as file:
-    exec(file.read(), version)
-
-setup(
-    name="pykeepass",
-    version=version["__version__"],
-    license="GPL3",
-    description="Python library to interact with keepass databases "
-    "(supports KDBX3 and KDBX4)",
-    long_description=README,
-    long_description_content_type='text/x-rst',
-    author="Philipp Schmitt",
-    author_email="philipp@schmitt.co",
-    url="https://github.com/libkeepass/pykeepass",
-    packages=find_packages(include=['pykeepass', 'pykeepass.*']),
-    install_requires=[
-        "python-dateutil",
-        "construct",
-        "argon2_cffi",
-        "pycryptodomex>=3.6.2",
-        "lxml",
-    ],
-    include_package_data=True,
-)
diff --git a/tests/tests.py b/tests/tests.py
index 7ae2f98b..9f7e4daa 100644
--- a/tests/tests.py
+++ b/tests/tests.py
@@ -5,9 +5,8 @@
 import shutil
 import unittest
 import uuid
-from datetime import datetime, timedelta
+from datetime import datetime, timedelta, timezone
 
-from dateutil import tz
 from pathlib import Path
 
 from io import BytesIO
@@ -222,7 +221,7 @@ def test_history_group(self):
 
     def test_add_delete_move_entry(self):
         unique_str = 'test_add_entry_'
-        expiry_time = datetime.now()
+        expiry_time = datetime.now(timezone.utc)
         entry = self.kp.add_entry(
             self.kp.root_group,
             unique_str + 'title',
@@ -246,8 +245,6 @@ def test_add_delete_move_entry(self):
         self.assertEqual(len(results.tags), 6)
         self.assertTrue(results.uuid != None)
         self.assertTrue(results.autotype_sequence is None)
-        # convert naive datetime to utc
-        expiry_time_utc = expiry_time.replace(tzinfo=tz.gettz()).astimezone(tz.gettz('UTC'))
         self.assertEqual(results.icon, icons.KEY)
 
         sub_group = self.kp.add_group(self.kp.root_group, 'sub_group')
@@ -283,6 +280,52 @@ def test_raise_exception_entry(self):
         )
         self.assertRaises(Exception, entry)
 
+    # ---------- Timezone test -----------
+
+    def test_expiration_time_tz(self):
+        # The expiration date is compared in UTC
+        # setting expiration date with tz offset 6 hours should result in expired entry
+        unique_str = 'test_exptime_tz_1_'
+        expiry_time = datetime.now(timezone(offset=timedelta(hours=6))).replace(microsecond=0)
+        self.kp.add_entry(
+            self.kp.root_group,
+            unique_str + 'title',
+            unique_str + 'user',
+            unique_str + 'pass',
+            expiry_time=expiry_time
+        )
+        results = self.kp.find_entries_by_title(unique_str + 'title', first=True)
+        self.assertEqual(results.expired, True)
+        self.assertEqual(results.expiry_time, expiry_time.astimezone(timezone.utc))
+
+        # setting expiration date with UTC tz should result in expired entry
+        unique_str = 'test_exptime_tz_2_'
+        expiry_time = datetime.now(timezone.utc).replace(microsecond=0)
+        self.kp.add_entry(
+            self.kp.root_group,
+            unique_str + 'title',
+            unique_str + 'user',
+            unique_str + 'pass',
+            expiry_time=expiry_time
+        )
+        results = self.kp.find_entries_by_title(unique_str + 'title', first=True)
+        self.assertEqual(results.expired, True)
+        self.assertEqual(results.expiry_time, expiry_time.astimezone(timezone.utc))
+
+        # setting expiration date with tz offset -6 hours while adding 6 hours should result in valid entry
+        unique_str = 'test_exptime_tz_3_'
+        expiry_time = datetime.now(timezone(offset=timedelta(hours=-6))).replace(microsecond=0) + timedelta(hours=6)
+        self.kp.add_entry(
+            self.kp.root_group,
+            unique_str + 'title',
+            unique_str + 'user',
+            unique_str + 'pass',
+            expiry_time=expiry_time
+        )
+        results = self.kp.find_entries_by_title(unique_str + 'title', first=True)
+        self.assertEqual(results.expired, False)
+        self.assertEqual(results.expiry_time, expiry_time.astimezone(timezone.utc))
+
     # ---------- Entries representation -----------
 
     def test_print_entries(self):
@@ -433,7 +476,7 @@ def test_recyclebinemptying(self):
 class EntryTests3(KDBX3Tests):
 
     def test_fields(self):
-        time = datetime.now().replace(microsecond=0)
+        expiry_time = datetime.now(timezone.utc).replace(microsecond=0)
         entry = Entry(
             'title',
             'username',
@@ -443,7 +486,7 @@ def test_fields(self):
             tags='tags',
             otp='otp',
             expires=True,
-            expiry_time=time,
+            expiry_time=expiry_time,
             icon=icons.KEY,
             kp=self.kp
         )
@@ -456,8 +499,7 @@ def test_fields(self):
         self.assertEqual(entry.tags, ['tags'])
         self.assertEqual(entry.otp, 'otp')
         self.assertEqual(entry.expires, True)
-        self.assertEqual(entry.expiry_time,
-                         time.replace(tzinfo=tz.gettz()).astimezone(tz.gettz('UTC')))
+        self.assertEqual(entry.expiry_time, expiry_time)
         self.assertEqual(entry.icon, icons.KEY)
         self.assertEqual(entry.is_a_history_entry, False)
         self.assertEqual(
@@ -487,7 +529,7 @@ def test_references(self):
         self.assertNotEqual(clone1, clone2)
 
     def test_set_and_get_fields(self):
-        time = datetime.now().replace(microsecond=0)
+        time = datetime.now(timezone.utc).replace(microsecond=0)
         changed_time = time + timedelta(hours=9)
         changed_string = 'changed_'
         entry = Entry(
@@ -528,8 +570,7 @@ def test_set_and_get_fields(self):
         self.assertEqual(entry.get_custom_property('foo'), None)
         # test time properties
         self.assertEqual(entry.expires, False)
-        self.assertEqual(entry.expiry_time,
-                         changed_time.replace(tzinfo=tz.gettz()).astimezone(tz.gettz('UTC')))
+        self.assertEqual(entry.expiry_time, changed_time)
 
         entry.tags = 'changed_tags'
         self.assertEqual(entry.tags, ['changed_tags'])
@@ -540,8 +581,8 @@ def test_set_and_get_fields(self):
 
     def test_expired_datetime_offset(self):
         """Test for https://github.com/pschmitt/pykeepass/issues/115"""
-        future_time = datetime.now() + timedelta(days=1)
-        past_time = datetime.now() - timedelta(days=1)
+        future_time = datetime.now(timezone.utc) + timedelta(days=1)
+        past_time = datetime.now(timezone.utc) - timedelta(days=1)
         entry = Entry(
             'title',
             'username',
@@ -695,7 +736,7 @@ def test_find_history_entries(self):
 
         # change the active entries to test integrity of the history items
         backup = {}
-        now = datetime.now()
+        now = datetime.now(timezone.utc)
         for entry in res1:
             backup[entry.uuid] = {"atime": entry.atime, "mtime": entry.mtime, "ctime": entry.ctime}
             entry.title = changed + 'title'
@@ -863,8 +904,8 @@ def test_credchange(self):
 
         required_days = 5
         recommended_days = 5
-        unexpired_date = datetime.now() - timedelta(days=1)
-        expired_date = datetime.now() - timedelta(days=10)
+        unexpired_date = datetime.now(timezone.utc) - timedelta(days=1)
+        expired_date = datetime.now(timezone.utc) - timedelta(days=10)
 
         self.kp.credchange_required_days = required_days
         self.kp.credchange_recommended_days = recommended_days