diff --git a/CHANGES.rst b/CHANGES.rst
index a0b0e009c..ee831be6a 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -25,6 +25,7 @@ The ASDF Standard is at v1.6.0
   ``asdf.tags.core.Stream``, update block storage support for
   Converter and update internal block API [#1537]
 - Remove deprecated resolve_local_refs argument to load_schema [#1623]
+- Add support for python 3.12 [#1641]
 
 2.15.1 (2023-08-07)
 -------------------
diff --git a/asdf/asdf.py b/asdf/asdf.py
index 3c2890ebc..8414953e9 100644
--- a/asdf/asdf.py
+++ b/asdf/asdf.py
@@ -1336,8 +1336,8 @@ def add_history_entry(self, description, software=None):
         elif software is not None:
             software = Software(software)
 
-        time_ = datetime.datetime.utcfromtimestamp(
-            int(os.environ.get("SOURCE_DATE_EPOCH", time.time())),
+        time_ = datetime.datetime.fromtimestamp(
+            int(os.environ.get("SOURCE_DATE_EPOCH", time.time())), datetime.timezone.utc
         )
 
         entry = HistoryEntry(
diff --git a/pyproject.toml b/pyproject.toml
index 8c06773f5..eef720ff3 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -13,6 +13,7 @@ classifiers = [
   'Programming Language :: Python :: 3.9',
   'Programming Language :: Python :: 3.10',
   'Programming Language :: Python :: 3.11',
+  'Programming Language :: Python :: 3.12',
 ]
 dynamic = [
   'version',