diff --git a/.github/ISSUE_TEMPLATE/bug_report.md b/.github/ISSUE_TEMPLATE/bug_report.md
index da7d163a..db0957c4 100644
--- a/.github/ISSUE_TEMPLATE/bug_report.md
+++ b/.github/ISSUE_TEMPLATE/bug_report.md
@@ -50,7 +50,7 @@ If applicable, add screenshots to help explain your problem.
 
 - OS: [e.g. Linux/Windows/MacOS]
 - GCSA version: [e.g. 2.0.1]
-- Python version: [e.g. 3.11]
+- Python version: [e.g. 3.12]
 
 ## Additional context
 
diff --git a/.github/workflows/code-cov.yml b/.github/workflows/code-cov.yml
index b7c929a1..b8b07bbd 100644
--- a/.github/workflows/code-cov.yml
+++ b/.github/workflows/code-cov.yml
@@ -13,7 +13,7 @@ jobs:
       - name: Set up Python
         uses: actions/setup-python@v2
         with:
-          python-version: '3.11'
+          python-version: '3.12'
 
       - name: Install dependencies
         run: pip install tox
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 717bc108..9fd1249b 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -12,9 +12,9 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: [ '3.7', '3.8', '3.9', '3.10', '3.11' ]
+        python-version: [ '3.7', '3.8', '3.9', '3.10', '3.11', '3.12' ]
         include:
-          - python-version: '3.11'
+          - python-version: '3.12'
             note: with-style-and-docs-checks
 
     steps:
diff --git a/.gitignore b/.gitignore
index a5013b18..fd8db29a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -9,6 +9,7 @@ build
 dist
 .eggs
 gcsa.egg-info
+docs/html
 
 example.py
 coverage.xml
diff --git a/.readthedocs.yml b/.readthedocs.yml
index 2107520f..e520e314 100644
--- a/.readthedocs.yml
+++ b/.readthedocs.yml
@@ -3,7 +3,7 @@ version: 2
 build:
   os: ubuntu-22.04
   tools:
-    python: "3.11"
+    python: "3.12"
 
 sphinx:
   configuration: docs/source/conf.py
diff --git a/docs/source/attendees.rst b/docs/source/attendees.rst
index 7c6e72a7..b5ef8f84 100644
--- a/docs/source/attendees.rst
+++ b/docs/source/attendees.rst
@@ -61,5 +61,21 @@ or
 
     event.add_attendee('attendee@gmail.com')
 
+to add a single attendee.
+
+Use :py:meth:`~gcsa.event.Event.add_attendees` method to add multiple at once:
+
+.. code-block:: python
+
+    event.add_attendees(
+        [
+            Attendee('attendee@gmail.com',
+                display_name='Friend',
+                additional_guests=3
+            ),
+            'attendee_by_email1@gmail.com',
+            'attendee_by_email2@gmail.com'
+        ]
+    )
 
 Update event using :py:meth:`~gcsa.google_calendar.GoogleCalendar.update_event` method to save the changes.
diff --git a/docs/source/change_log.rst b/docs/source/change_log.rst
index fdd2ec7d..dcb9ce28 100644
--- a/docs/source/change_log.rst
+++ b/docs/source/change_log.rst
@@ -3,6 +3,26 @@
 Change log
 ==========
 
+v2.3.0
+~~~~~~
+
+API
+---
+* Adds `add_attendees` method to the `Event` for adding multiple attendees
+* Add specific time reminders (N days before at HH:MM)
+* Support Python3.12
+* Allow service account credentials in `GoogleCalendar`
+
+Core
+----
+* Don't evaluate default arguments in code docs (primarily for `timezone=get_localzone_name()`)
+
+Backward compatibility
+----------------------
+* If token is expired but doesn't have refresh token, raises `google.auth.exceptions.RefreshError`
+  instead of sending the request
+
+
 v2.2.0
 ~~~~~~
 
diff --git a/docs/source/conf.py b/docs/source/conf.py
index e92cb3ec..1e78fefe 100644
--- a/docs/source/conf.py
+++ b/docs/source/conf.py
@@ -186,3 +186,5 @@
     'css/custom.css',
     'css/colors.css',
 ]
+
+autodoc_preserve_defaults = True
diff --git a/docs/source/reminders.rst b/docs/source/reminders.rst
index cb595020..764b641f 100644
--- a/docs/source/reminders.rst
+++ b/docs/source/reminders.rst
@@ -56,3 +56,60 @@ To use default reminders of the calendar, set ``default_reminders`` parameter of
 to ``True``.
 
 .. note:: You can add up to 5 reminders to one event.
+
+Specific time reminders
+~~~~~~~~~~~~~~~~~~~~~~~
+
+You can also set specific time for a reminder.
+
+.. code-block:: python
+
+    from datetime import time
+
+    event = Event(
+        'Meeting',
+        start=(22/Apr/2019)[12:00],
+        reminders=[
+            # Day before the event at 13:30
+            EmailReminder(days_before=1, at=time(13, 30)),
+            # 2 days before the event at 19:15
+            PopupReminder(days_before=2, at=time(19, 15))
+        ]
+    )
+
+    event.add_popup_reminder(days_before=3, at=time(8, 30))
+    event.add_email_reminder(days_before=4, at=time(9, 0))
+
+
+.. note:: Google calendar API only works with ``minutes_before_start``.
+    The GCSA's interface that uses ``days_before`` and ``at`` arguments is only a convenient way of setting specific time.
+    GCSA will convert ``days_before`` and ``at`` to ``minutes_before_start`` during API requests.
+    So after you add or update the event, it will have reminders with only ``minutes_before_start`` set even if they
+    were initially created with ``days_before`` and ``at``.
+
+    .. code-block:: python
+
+        from datetime import time
+
+        event = Event(
+            'Meeting',
+            start=(22/Apr/2019)[12:00],
+            reminders=[
+                # Day before the event at 12:00
+                EmailReminder(days_before=1, at=time(12, 00))
+            ]
+        )
+
+        event.reminders[0].minutes_before_start is None
+        event.reminders[0].days_before == 1
+        event.reminders[0].at == time(12, 00)
+
+        event = gc.add_event(event)
+
+        event.reminders[0].minutes_before_start == 24 * 60  # exactly one day before
+        event.reminders[0].days_before is None
+        event.reminders[0].at is None
+
+    GCSA does not convert ``minutes_before_start`` to ``days_before`` and ``at`` (even for the whole-day events)
+    for backwards compatibility reasons.
+
diff --git a/gcsa/_services/authentication.py b/gcsa/_services/authentication.py
index 0fb04c90..20582292 100644
--- a/gcsa/_services/authentication.py
+++ b/gcsa/_services/authentication.py
@@ -6,7 +6,7 @@
 from googleapiclient import discovery
 from google_auth_oauthlib.flow import InstalledAppFlow
 from google.auth.transport.requests import Request
-from google.oauth2.credentials import Credentials
+from google.auth.credentials import Credentials
 
 
 class AuthenticatedService:
@@ -24,7 +24,8 @@ def __init__(
             save_token: bool = True,
             read_only: bool = False,
             authentication_flow_host: str = 'localhost',
-            authentication_flow_port: int = 8080
+            authentication_flow_port: int = 8080,
+            authentication_flow_bind_addr: str = None
     ):
         """
         Specify ``credentials`` to use in requests or ``credentials_path`` and ``token_path`` to get credentials from.
@@ -49,6 +50,9 @@ def __init__(
                 Host to receive response during authentication flow
         :param authentication_flow_port:
                 Port to receive response during authentication flow
+        :param authentication_flow_bind_addr:
+                Optional IP address for the redirect server to listen on when it is not the same as host
+                (e.g. in a container)
         """
 
         if credentials:
@@ -66,7 +70,8 @@ def __init__(
                 scopes,
                 save_token,
                 authentication_flow_host,
-                authentication_flow_port
+                authentication_flow_port,
+                authentication_flow_bind_addr
             )
 
         self.service = discovery.build('calendar', 'v3', credentials=self.credentials)
@@ -75,7 +80,7 @@ def __init__(
     def _ensure_refreshed(
             credentials: Credentials
     ) -> Credentials:
-        if not credentials.valid and credentials.expired and credentials.refresh_token:
+        if not credentials.valid and credentials.expired:
             credentials.refresh(Request())
         return credentials
 
@@ -87,7 +92,8 @@ def _get_credentials(
             scopes: List[str],
             save_token: bool,
             host: str,
-            port: int
+            port: int,
+            bind_addr: str
     ) -> Credentials:
         credentials = None
 
@@ -101,7 +107,7 @@ def _get_credentials(
             else:
                 credentials_path = os.path.join(credentials_dir, credentials_file)
                 flow = InstalledAppFlow.from_client_secrets_file(credentials_path, scopes)
-                credentials = flow.run_local_server(host=host, port=port)
+                credentials = flow.run_local_server(host=host, port=port, bind_addr=bind_addr)
 
             if save_token:
                 with open(token_path, 'wb') as token_file:
diff --git a/gcsa/event.py b/gcsa/event.py
index e3ed1047..b6c547bb 100644
--- a/gcsa/event.py
+++ b/gcsa/event.py
@@ -3,7 +3,7 @@
 
 from beautiful_date import BeautifulDate
 from tzlocal import get_localzone_name
-from datetime import datetime, date, timedelta
+from datetime import datetime, date, timedelta, time
 
 from ._resource import Resource
 from .attachment import Attachment
@@ -223,6 +223,15 @@ def add_attendee(
         Attendee may be given as email string or :py:class:`~gcsa.attendee.Attendee` object."""
         self.attendees.append(self._ensure_attendee_from_email(attendee))
 
+    def add_attendees(
+            self,
+            attendees: List[Union[str, Attendee]]
+    ):
+        """Adds multiple attendees to an event. See :py:class:`~gcsa.attendee.Attendee`.
+        Each attendee may be given as email string or :py:class:`~gcsa.attendee.Attendee` object."""
+        for a in attendees:
+            self.add_attendee(a)
+
     def add_attachment(
             self,
             file_url: str,
@@ -234,17 +243,21 @@ def add_attachment(
 
     def add_email_reminder(
             self,
-            minutes_before_start: int = 60
+            minutes_before_start: int = None,
+            days_before: int = None,
+            at: time = None
     ):
         """Adds email reminder to an event. See :py:class:`~gcsa.reminders.EmailReminder`"""
-        self.add_reminder(EmailReminder(minutes_before_start))
+        self.add_reminder(EmailReminder(minutes_before_start, days_before, at))
 
     def add_popup_reminder(
             self,
-            minutes_before_start: int = 30
+            minutes_before_start: int = None,
+            days_before: int = None,
+            at: time = None
     ):
         """Adds popup reminder to an event. See :py:class:`~gcsa.reminders.PopupReminder`"""
-        self.add_reminder(PopupReminder(minutes_before_start))
+        self.add_reminder(PopupReminder(minutes_before_start, days_before, at))
 
     def add_reminder(
             self,
diff --git a/gcsa/google_calendar.py b/gcsa/google_calendar.py
index 3356c579..592c620b 100644
--- a/gcsa/google_calendar.py
+++ b/gcsa/google_calendar.py
@@ -30,7 +30,8 @@ def __init__(
             save_token: bool = True,
             read_only: bool = False,
             authentication_flow_host: str = 'localhost',
-            authentication_flow_port: int = 8080
+            authentication_flow_port: int = 8080,
+            authentication_flow_bind_addr: str = None
     ):
         """
         Specify ``credentials`` to use in requests or ``credentials_path`` and ``token_path`` to get credentials from.
@@ -63,6 +64,9 @@ def __init__(
                 Host to receive response during authentication flow
         :param authentication_flow_port:
                 Port to receive response during authentication flow
+        :param authentication_flow_bind_addr:
+                Optional IP address for the redirect server to listen on when it is not the same as host
+                (e.g. in a container)
         """
         super().__init__(
             default_calendar=default_calendar,
@@ -72,5 +76,6 @@ def __init__(
             save_token=save_token,
             read_only=read_only,
             authentication_flow_host=authentication_flow_host,
-            authentication_flow_port=authentication_flow_port
+            authentication_flow_port=authentication_flow_port,
+            authentication_flow_bind_addr=authentication_flow_bind_addr
         )
diff --git a/gcsa/reminders.py b/gcsa/reminders.py
index b13dcdc6..2d32d56e 100644
--- a/gcsa/reminders.py
+++ b/gcsa/reminders.py
@@ -1,54 +1,137 @@
+from datetime import time, date, datetime
+from typing import Union
+
+from beautiful_date import BeautifulDate, days
+
+
 class Reminder:
     def __init__(
             self,
             method: str,
-            minutes_before_start: int
+            minutes_before_start: int = None,
+            days_before: int = None,
+            at: time = None
     ):
         """Represents base reminder object
 
+        Provide `minutes_before_start` to create "relative" reminder.
+        Provide `days_before` and `at` to create "absolute" reminder.
+
         :param method:
                 Method of the reminder. Possible values: email or popup
         :param minutes_before_start:
                 Minutes before reminder
+        :param days_before:
+                Days before reminder
+        :param at:
+                Specific time for a reminder
         """
+        # Nothing was provided
+        if minutes_before_start is None and days_before is None and at is None:
+            raise ValueError("Relative reminder needs 'minutes_before_start'. "
+                             "Absolute reminder 'days_before' and 'at' set. "
+                             "None of them were provided.")
+
+        # Both minutes_before_start and days_before/at were provided
+        if minutes_before_start is not None and (days_before is not None or at is not None):
+            raise ValueError("Only minutes_before_start or days_before/at can be specified.")
+
+        # Only one of days_before and at was provided
+        if (days_before is None) != (at is None):
+            raise ValueError(f'Both "days_before" and "at" values need to be set '
+                             f'when using absolute time for a reminder. '
+                             f'Provided days_before={days_before} and at={at}.')
+
         self.method = method
         self.minutes_before_start = minutes_before_start
+        self.days_before = days_before
+        self.at = at
 
     def __eq__(self, other):
         return (
                 isinstance(other, Reminder)
                 and self.method == other.method
                 and self.minutes_before_start == other.minutes_before_start
+                and self.days_before == other.days_before
+                and self.at == other.at
         )
 
     def __str__(self):
-        return '{} - minutes_before_start:{}'.format(self.__class__.__name__, self.minutes_before_start)
+        if self.minutes_before_start is not None:
+            return '{} - minutes_before_start:{}'.format(self.__class__.__name__, self.minutes_before_start)
+        else:
+            return '{} - {} days before at {}'.format(self.__class__.__name__, self.days_before, self.at)
 
     def __repr__(self):
         return '<{}>'.format(self.__str__())
 
+    def convert_to_relative(self, start: Union[date, datetime, BeautifulDate]) -> 'Reminder':
+        """Converts absolute reminder (with set `days_before` and `at`) to relative (with set `minutes_before_start`)
+         relative to `start` date/datetime. Returns self if `minutes_before_start` already set.
+         """
+        if self.minutes_before_start is not None:
+            return self
+
+        tzinfo = start.tzinfo if isinstance(start, datetime) else None
+        start_of_the_day = datetime.combine(start, datetime.min.time(), tzinfo=tzinfo)
+
+        reminder_tzinfo = self.at.tzinfo or tzinfo
+        reminder_time = datetime.combine(start_of_the_day - self.days_before * days, self.at, tzinfo=reminder_tzinfo)
+
+        if isinstance(start, datetime):
+            minutes_before_start = int((start - reminder_time).total_seconds() / 60)
+        else:
+            minutes_before_start = int((start_of_the_day - reminder_time).total_seconds() / 60)
+
+        return Reminder(
+            method=self.method,
+            minutes_before_start=minutes_before_start
+        )
+
 
 class EmailReminder(Reminder):
     def __init__(
             self,
-            minutes_before_start: int = 60
+            minutes_before_start: int = None,
+            days_before: int = None,
+            at: time = None
     ):
         """Represents email reminder object
 
+        Provide `minutes_before_start` to create "relative" reminder.
+        Provide `days_before` and `at` to create "absolute" reminder.
+
         :param minutes_before_start:
                 Minutes before reminder
+        :param days_before:
+                Days before reminder
+        :param at:
+                Specific time for a reminder
         """
-        super().__init__('email', minutes_before_start)
+        if not days_before and not at and not minutes_before_start:
+            minutes_before_start = 60
+        super().__init__('email', minutes_before_start, days_before, at)
 
 
 class PopupReminder(Reminder):
     def __init__(
             self,
-            minutes_before_start: int = 30
+            minutes_before_start: int = None,
+            days_before: int = None,
+            at: time = None
     ):
         """Represents popup reminder object
 
+        Provide `minutes_before_start` to create "relative" reminder.
+        Provide `days_before` and `at` to create "absolute" reminder.
+
         :param minutes_before_start:
                 Minutes before reminder
+        :param days_before:
+                Days before reminder
+        :param at:
+                Specific time for a reminder
         """
-        super().__init__('popup', minutes_before_start)
+        if not days_before and not at and not minutes_before_start:
+            minutes_before_start = 30
+        super().__init__('popup', minutes_before_start, days_before, at)
diff --git a/gcsa/serializers/event_serializer.py b/gcsa/serializers/event_serializer.py
index f108fd6e..f2f9cb37 100644
--- a/gcsa/serializers/event_serializer.py
+++ b/gcsa/serializers/event_serializer.py
@@ -33,10 +33,6 @@ def _to_json(cls, event: Event):
             'guestsCanModify': event.guests_can_modify,
             'guestsCanSeeOtherGuests': event.guests_can_see_other_guests,
             'transparency': event.transparency,
-            'reminders': {
-                'useDefault': event.default_reminders,
-                'overrides': [ReminderSerializer.to_json(r) for r in event.reminders]
-            },
             'attachments': [AttachmentSerializer.to_json(a) for a in event.attachments],
             **event.other
         }
@@ -54,16 +50,14 @@ def _to_json(cls, event: Event):
             data['start'] = {'date': event.start.isoformat()}
             data['end'] = {'date': event.end.isoformat()}
 
-        if event.default_reminders:
-            data['reminders'] = {
-                'useDefault': True
-            }
-        else:
-            data['reminders'] = {
-                'useDefault': False
-            }
-            if event.reminders:
-                data['reminders']['overrides'] = [ReminderSerializer.to_json(r) for r in event.reminders]
+        data['reminders'] = {
+            'useDefault': event.default_reminders
+        }
+        if event.reminders:
+            data['reminders']['overrides'] = [
+                ReminderSerializer.to_json(r.convert_to_relative(event.start))
+                for r in event.reminders
+            ]
 
         if event.conference_solution is not None:
             if isinstance(event.conference_solution, ConferenceSolution):
diff --git a/setup.py b/setup.py
index fff15521..eb30b70e 100755
--- a/setup.py
+++ b/setup.py
@@ -1,22 +1,14 @@
 #!/usr/bin/env python3
+import subprocess
 
 from setuptools import setup, find_packages, Command
 from shutil import rmtree
 import os
 import sys
 
-try:
-    from sphinx.setup_command import BuildDoc
-except ImportError:
-    class BuildDoc(Command):
-        user_options = []
-
-        def run(self):
-            raise
-
 here = os.path.abspath(os.path.dirname(__file__))
 
-VERSION = '2.2.0'
+VERSION = '2.3.0'
 
 
 class UploadCommand(Command):
@@ -60,6 +52,49 @@ def run(self):
         sys.exit()
 
 
+class BuildDoc(Command):
+    user_options = []
+
+    def initialize_options(self) -> None:
+        pass
+
+    def finalize_options(self) -> None:
+        pass
+
+    def run(self):
+        output_path = 'docs/html'
+        changed_files = []
+        cmd = [
+            'sphinx-build',
+            'docs/source', output_path,
+            '--builder', 'html',
+            '--define', f'version={VERSION}',
+            '--verbose'
+        ]
+        with subprocess.Popen(
+                cmd,
+                stdout=subprocess.PIPE,
+                bufsize=1,
+                universal_newlines=True
+        ) as p:
+            for line in p.stdout:
+                print(line, end='')
+                if line.startswith('reading sources... ['):
+                    file_name = line.rsplit(maxsplit=1)[1]
+                    if file_name:
+                        changed_files.append(file_name + '.html')
+
+        index_path = os.path.join(os.getcwd(), output_path, 'index.html')
+        print('\nIndex:')
+        print(f'file://{index_path}')
+
+        if changed_files:
+            print('Update pages:')
+            for cf in changed_files:
+                f_path = os.path.join(os.getcwd(), output_path, cf)
+                print(cf, f'file://{f_path}')
+
+
 with open('README.rst') as f:
     long_description = ''.join(f.readlines())
 
@@ -97,7 +132,7 @@ def run(self):
         "tzlocal>=4,<5",
         "google-api-python-client>=1.8",
         "google-auth-httplib2>=0.0.4",
-        "google-auth-oauthlib>=0.5,<1.0",
+        "google-auth-oauthlib>=0.5,<2.0",
         "python-dateutil>=2.7",
         "beautiful_date>=2.0.0",
     ],
@@ -121,15 +156,10 @@ def run(self):
         'Programming Language :: Python :: 3.9',
         'Programming Language :: Python :: 3.10',
         'Programming Language :: Python :: 3.11',
+        'Programming Language :: Python :: 3.12',
     ],
     cmdclass={
         'upload': UploadCommand,
         'docs': BuildDoc,
-    },
-    command_options={
-        'docs': {
-            'version': ('setup.py', VERSION),
-            'build_dir': ('setup.py', 'docs/build')
-        }
-    },
+    }
 )
diff --git a/tests/test_event.py b/tests/test_event.py
index 1480faca..786e464a 100644
--- a/tests/test_event.py
+++ b/tests/test_event.py
@@ -1,3 +1,4 @@
+from datetime import time
 from unittest import TestCase
 from beautiful_date import Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sept, Oct, Dec, hours, days, Nov
 
@@ -97,6 +98,18 @@ def test_add_reminders(self):
         self.assertIsInstance(e.reminders[1], PopupReminder)
         self.assertEqual(e.reminders[1].minutes_before_start, 41)
 
+        e.add_popup_reminder(days_before=1, at=time(12, 0))
+        self.assertEqual(len(e.reminders), 3)
+        self.assertIsInstance(e.reminders[2], PopupReminder)
+        self.assertEqual(e.reminders[2].days_before, 1)
+        self.assertEqual(e.reminders[2].at, time(12, 0))
+
+        e.add_email_reminder(days_before=1, at=time(13, 30))
+        self.assertEqual(len(e.reminders), 4)
+        self.assertIsInstance(e.reminders[3], EmailReminder)
+        self.assertEqual(e.reminders[3].days_before, 1)
+        self.assertEqual(e.reminders[3].at, time(13, 30))
+
     def test_add_attendees(self):
         e = Event('Good day',
                   start=(17 / Jul / 2020),
@@ -109,12 +122,18 @@ def test_add_attendees(self):
         self.assertEqual(len(e.attendees), 2)
         e.add_attendee(Attendee("attendee3@gmail.com"))
         e.add_attendee(Attendee(email="attendee4@gmail.com"))
-        self.assertEqual(len(e.attendees), 4)
+        e.add_attendees([
+            Attendee(email="attendee5@gmail.com"),
+            "attendee6@gmail.com"
+        ])
+        self.assertEqual(len(e.attendees), 6)
 
         self.assertEqual(e.attendees[0].email, "attendee@gmail.com")
         self.assertEqual(e.attendees[1].email, "attendee2@gmail.com")
         self.assertEqual(e.attendees[2].email, "attendee3@gmail.com")
         self.assertEqual(e.attendees[3].email, "attendee4@gmail.com")
+        self.assertEqual(e.attendees[4].email, "attendee5@gmail.com")
+        self.assertEqual(e.attendees[5].email, "attendee6@gmail.com")
 
     def test_reminders_checks(self):
         with self.assertRaises(ValueError):
@@ -350,6 +369,38 @@ def test_to_json_reminders(self):
         }
         self.assertDictEqual(EventSerializer.to_json(e), expected_event_json)
 
+        e = Event('Good day',
+                  start=(1 / Jan / 2019)[11:22:33],
+                  timezone=TEST_TIMEZONE,
+                  reminders=[
+                      PopupReminder(35),
+                      EmailReminder(45),
+                      PopupReminder(days_before=3, at=time(12, 30)),
+                      EmailReminder(days_before=2, at=time(11, 25)),
+                  ])
+        expected_event_json = {
+            'summary': 'Good day',
+            'start': {'dateTime': '2019-01-01T11:22:33+13:00', 'timeZone': TEST_TIMEZONE},
+            'end': {'dateTime': '2019-01-01T12:22:33+13:00', 'timeZone': TEST_TIMEZONE},
+            'recurrence': [],
+            'visibility': 'default',
+            'attendees': [],
+            'reminders': {
+                'overrides': [
+                    {'method': 'popup', 'minutes': 35},
+                    {'method': 'email', 'minutes': 45},
+                    {'method': 'popup', 'minutes': (11 * 60 + 22) + (2 * 24 * 60 + 11 * 60 + 30)},
+                    {'method': 'email', 'minutes': (11 * 60 + 22) + (1 * 24 * 60 + 12 * 60 + 35)},
+                ],
+                'useDefault': False
+            },
+            'attachments': [],
+            'guestsCanInviteOthers': True,
+            'guestsCanModify': False,
+            'guestsCanSeeOtherGuests': True,
+        }
+        self.assertDictEqual(EventSerializer.to_json(e), expected_event_json)
+
     def test_to_json_attendees(self):
         e = Event('Good day',
                   start=(1 / Jul / 2020)[11:22:33],
diff --git a/tests/test_reminder.py b/tests/test_reminder.py
index 8ab333fd..73978757 100644
--- a/tests/test_reminder.py
+++ b/tests/test_reminder.py
@@ -1,25 +1,89 @@
+from datetime import time, datetime, date
 from unittest import TestCase
 
-from gcsa.reminders import EmailReminder, PopupReminder
+from beautiful_date import Apr
+
+from gcsa.reminders import Reminder, EmailReminder, PopupReminder
 from gcsa.serializers.reminder_serializer import ReminderSerializer
 
 
 class TestReminder(TestCase):
     def test_email_reminder(self):
+        reminder = EmailReminder()
+        self.assertEqual(reminder.method, 'email')
+        self.assertEqual(reminder.minutes_before_start, 60)
+
         reminder = EmailReminder(34)
         self.assertEqual(reminder.method, 'email')
         self.assertEqual(reminder.minutes_before_start, 34)
 
+        reminder = EmailReminder(days_before=1, at=time(0, 0))
+        self.assertEqual(reminder.method, 'email')
+        self.assertEqual(reminder.minutes_before_start, None)
+        self.assertEqual(reminder.days_before, 1)
+        self.assertEqual(reminder.at, time(0, 0))
+
     def test_popup_reminder(self):
+        reminder = PopupReminder()
+        self.assertEqual(reminder.method, 'popup')
+        self.assertEqual(reminder.minutes_before_start, 30)
+
         reminder = PopupReminder(51)
         self.assertEqual(reminder.method, 'popup')
         self.assertEqual(reminder.minutes_before_start, 51)
 
+        reminder = PopupReminder(days_before=1, at=time(0, 0))
+        self.assertEqual(reminder.method, 'popup')
+        self.assertEqual(reminder.minutes_before_start, None)
+        self.assertEqual(reminder.days_before, 1)
+        self.assertEqual(reminder.at, time(0, 0))
+
     def test_repr_str(self):
         reminder = EmailReminder(34)
         self.assertEqual(reminder.__repr__(), "<EmailReminder - minutes_before_start:34>")
         self.assertEqual(reminder.__str__(), "EmailReminder - minutes_before_start:34")
 
+        reminder = PopupReminder(days_before=1, at=time(0, 0))
+        self.assertEqual(reminder.__repr__(), "<PopupReminder - 1 days before at 00:00:00>")
+        self.assertEqual(reminder.__str__(), "PopupReminder - 1 days before at 00:00:00")
+
+    def test_absolute_reminders_conversion(self):
+        absolute_reminder = EmailReminder(days_before=1, at=time(12, 0))
+        reminder = absolute_reminder.convert_to_relative(datetime(2024, 4, 16, 10, 15))
+        self.assertEqual(reminder.method, 'email')
+        self.assertEqual(reminder.minutes_before_start, (12 + 10) * 60 + 15)
+
+        absolute_reminder = PopupReminder(days_before=2, at=time(11, 30))
+        reminder = absolute_reminder.convert_to_relative(date(2024, 4, 16))
+        self.assertEqual(reminder.method, 'popup')
+        self.assertEqual(reminder.minutes_before_start, 24 * 60 + 12 * 60 + 30)
+
+        absolute_reminder = PopupReminder(days_before=5, at=time(10, 25))
+        reminder = absolute_reminder.convert_to_relative(16 / Apr / 2024)
+        self.assertEqual(reminder.method, 'popup')
+        self.assertEqual(reminder.minutes_before_start, 4 * 24 * 60 + 13 * 60 + 35)
+
+    def test_reminder_checks(self):
+        # No time provided
+        with self.assertRaises(ValueError):
+            Reminder(method='email')
+
+        # Both relative and absolute times provided
+        with self.assertRaises(ValueError):
+            Reminder(method='email', minutes_before_start=22, days_before=1)
+        with self.assertRaises(ValueError):
+            Reminder(method='email', minutes_before_start=22, at=time(0, 0))
+
+        # Only one of days_before and at provided
+        with self.assertRaises(ValueError):
+            Reminder(method='email', days_before=1)
+        with self.assertRaises(ValueError):
+            Reminder(method='email', at=time(0, 0))
+        with self.assertRaises(ValueError):
+            PopupReminder(days_before=1)
+        with self.assertRaises(ValueError):
+            EmailReminder(at=time(0, 0))
+
 
 class TestReminderSerializer(TestCase):
     def test_to_json(self):
diff --git a/tox.ini b/tox.ini
index 1fc0cd49..4c88bef0 100644
--- a/tox.ini
+++ b/tox.ini
@@ -8,7 +8,8 @@ python =
     3.8: pytest
     3.9: pytest
     3.10: pytest
-    3.11: pytest, flake8, sphinx
+    3.11: pytest
+    3.12: pytest, flake8, sphinx
 
 [flake8]
 max-line-length = 120