diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 0997fac..66cf62d 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -11,11 +11,11 @@ permissions:
 
 jobs:
   test:
-    name: Test - Python ${{ matrix.python-version }}
-    runs-on: ubuntu-latest
+    runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        python-version: ["3.9", "3.10", "3.11", "3.12", "3.13"]
+        os: ["ubuntu-latest", "macos-latest", "windows-latest"]
+        python-version: ["pypy3.11", "3.9", "3.10", "3.11", "3.12", "3.13"]
     env:
       UV_PYTHON: ${{ matrix.python-version }}
     steps:
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 5b811c0..534aee6 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -1,7 +1,7 @@
 ---
 repos:
   - repo: https://github.com/pre-commit/pre-commit-hooks
-    rev: v4.6.0
+    rev: v5.0.0
     hooks:
       - id: check-added-large-files
       - id: check-ast
@@ -15,7 +15,7 @@ repos:
       - id: trailing-whitespace
 
   - repo: https://github.com/asottile/pyupgrade
-    rev: v3.15.2
+    rev: v3.20.0
     hooks:
       - id: pyupgrade
-        args: [--py38-plus]
+        args: [--py39-plus]
diff --git a/pyproject.toml b/pyproject.toml
index f6c8e5a..c6e45bf 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -26,7 +26,9 @@ classifiers = [
     "Topic :: Software Development :: Libraries :: Python Modules",
 ]
 requires-python = "~=3.9"
-dependencies = []
+dependencies = [
+    "tzdata; sys_platform == 'win32'",
+]
 
 [project.urls]
 Homepage = "https://github.com/getpelican/feedgenerator"
diff --git a/tests/test_feedgenerator.py b/tests/test_feedgenerator.py
index c389b54..7845378 100644
--- a/tests/test_feedgenerator.py
+++ b/tests/test_feedgenerator.py
@@ -1,9 +1,13 @@
 import datetime
+from zoneinfo import ZoneInfo
 
 import pytest
 
 import feedgenerator
 
+AWARE_DATE = datetime.datetime(2016,8,11,0,0,0,0,tzinfo=ZoneInfo("America/New_York"))
+AWARE_DATE_UTC = datetime.datetime(2016,8,11,0,0,0,0,tzinfo=ZoneInfo("UTC"))
+NAIVE_DATE = datetime.datetime(2016,8,11,0,0,0,0)
 
 FIXT_FEED = dict(
     title="Poynter E-Media Tidbits",
@@ -20,7 +24,7 @@
     link="http://www.holovaty.com/täst/",
     description="Testing.",
     content="Full content of our testing entry.",
-    pubdate=datetime.datetime(2016,8,11,0,0,0,0),
+    pubdate=NAIVE_DATE,
 )
 
 
@@ -135,3 +139,26 @@ def test_subtitle(description, subtitle, fragment, nonfragment):
         assert fragment in result
     if nonfragment:
         assert nonfragment not in result
+
+@pytest.mark.parametrize("generator, date, expected_date_string", [
+    (feedgenerator.Atom1Feed, AWARE_DATE, "2016-08-11T00:00:00-04:00"),
+    (feedgenerator.Atom1Feed, AWARE_DATE_UTC, "2016-08-11T00:00:00+00:00"),
+    (feedgenerator.Atom1Feed, NAIVE_DATE, "2016-08-11T00:00:00Z"),
+    (feedgenerator.Rss201rev2Feed, AWARE_DATE, "Thu, 11 Aug 2016 00:00:00 -0400"),
+    (feedgenerator.Rss201rev2Feed, AWARE_DATE_UTC, "Thu, 11 Aug 2016 00:00:00 +0000"),
+    (feedgenerator.Rss201rev2Feed, NAIVE_DATE, "Thu, 11 Aug 2016 00:00:00 -0000"),
+    (feedgenerator.RssUserland091Feed, AWARE_DATE, "Thu, 11 Aug 2016 00:00:00 -0400"),
+    (feedgenerator.RssUserland091Feed, AWARE_DATE_UTC, "Thu, 11 Aug 2016 00:00:00 +0000"),
+    (feedgenerator.RssUserland091Feed, NAIVE_DATE, "Thu, 11 Aug 2016 00:00:00 -0000"),
+    ])
+def test_timezone_handling(generator, date, expected_date_string):
+    """
+    Test that dates are handled correctly in all Feed generators.
+    Also test special cases of no timezone given, vs timezone without offset
+    """
+
+    feed = generator(**FIXT_FEED)
+    feed.add_item(**(FIXT_ITEM | {'pubdate': date}))
+    result = feed.writeString(ENCODING)
+
+    assert expected_date_string in result