diff --git a/src/spdx_tools/spdx/datetime_conversions.py b/src/spdx_tools/spdx/datetime_conversions.py
index cce624d57..6f84c2cda 100644
--- a/src/spdx_tools/spdx/datetime_conversions.py
+++ b/src/spdx_tools/spdx/datetime_conversions.py
@@ -1,6 +1,8 @@
 # SPDX-FileCopyrightText: 2022 spdx contributors
 #
 # SPDX-License-Identifier: Apache-2.0
+import re
+import warnings
 from datetime import datetime, timezone
 
 
@@ -8,8 +10,19 @@ def datetime_from_str(date_str: str) -> datetime:
     if not isinstance(date_str, str):
         raise TypeError(f"Could not convert str to datetime, invalid type: {type(date_str).__name__}")
 
-    date = datetime.strptime(date_str, "%Y-%m-%dT%H:%M:%SZ")  # raises ValueError if format does not match
-    return date
+    if "." not in date_str:
+        return datetime.strptime(date_str, "%Y-%m-%dT%H:%M:%SZ")  # raises ValueError if format does not match
+
+    # Based on the https://www.w3.org/TR/xmlschema11-2/#dateTimeStamp
+    # The secondFrag allows fractional second notation as well.
+    # truncate the microsecond part
+    date_str = re.sub(r"\.\d*Z$", "Z", date_str)
+    warnings.warn(
+        "Invalid date format. Expected YYYY-MM-DDThh:mm:ssZ. Sub-second fractions have been discarded.",
+        category=UserWarning,
+        stacklevel=2,
+    )
+    return datetime.strptime(date_str, "%Y-%m-%dT%H:%M:%SZ")  # raises ValueError if format does not match
 
 
 def datetime_to_iso_string(date: datetime) -> str:
diff --git a/tests/spdx/test_datetime_conversions.py b/tests/spdx/test_datetime_conversions.py
index 3967d593b..068a13769 100644
--- a/tests/spdx/test_datetime_conversions.py
+++ b/tests/spdx/test_datetime_conversions.py
@@ -43,10 +43,13 @@ def test_local_datetime_to_iso_string():
 
 def test_datetime_from_str():
     date_str = "2010-03-04T05:45:11Z"
+    assert datetime_from_str(date_str) == datetime(2010, 3, 4, 5, 45, 11)
 
-    date = datetime_from_str(date_str)
+    date_str = "2010-03-04T05:45:11.0Z"
+    assert datetime_from_str(date_str) == datetime(2010, 3, 4, 5, 45, 11)
 
-    assert date == datetime(2010, 3, 4, 5, 45, 11)
+    date_str = "2010-03-04T05:45:11.123456789Z"
+    assert datetime_from_str(date_str) == datetime(2010, 3, 4, 5, 45, 11)
 
 
 @pytest.mark.parametrize(
diff --git a/tests/spdx3/writer/tag_value/test_write_document.py b/tests/spdx3/writer/tag_value/test_write_document.py
index 580c61b81..10d5d54c6 100644
--- a/tests/spdx3/writer/tag_value/test_write_document.py
+++ b/tests/spdx3/writer/tag_value/test_write_document.py
@@ -29,9 +29,7 @@ def test_render_creation_info():
     output_str = io.StringIO()
     write_spdx_document(spdx_document, text_output=output_str)
 
-    assert (
-        output_str.getvalue()
-        == """\
+    assert output_str.getvalue() == """\
 ## SPDX Document
 SPDXID: SPDXRef-FOO
 name: BAR
@@ -42,4 +40,3 @@ def test_render_creation_info():
   data license: CC0-1.0
 elements: 
 """  # noqa: W291 # elements: are printed with a space
-    )