Fix fractional seconds in RFC3339 timestamps

datadog_checks_base/changelog.d/25497.fixed

@@ -0,0 +1 @@
+Fix parsing RFC3339 timestamps with fractional seconds.

datadog_checks_base/datadog_checks/base/utils/date.py

@@ -64,7 +64,7 @@ def parse_rfc3339(s):
     for x in range(6):
         dt[x] = int(groups[x])
     if groups[6] is not None:
-        dt[6] = int(groups[6])
+        dt[6] = int(groups[6][1:7].ljust(6, '0'))
     tz = UTC
     if groups[7] is not None and groups[7] != 'Z' and groups[7] != 'z':
         tz_groups = _re_timezone.search(groups[7]).groups()

datadog_checks_base/tests/base/utils/test_date.py

@@ -0,0 +1,33 @@
+# (C) Datadog, Inc. 2026-present
+# All rights reserved
+# Licensed under a 3-clause BSD style license (see LICENSE)
+
+from datetime import datetime, timedelta, timezone
+
+import pytest
+
+from datadog_checks.base.utils.date import parse_rfc3339
+
+
+@pytest.mark.parametrize(
+    'fraction, microsecond',
+    [
+        ('', 0),
+        ('.0', 0),
+        ('.1', 100000),
+        ('.123', 123000),
+        ('.001', 1000),
+        ('.123456', 123456),
+        ('.000001', 1),
+        ('.123456789', 123456),
+        ('.999999999', 999999),
+        ('.000000001', 0),
+        (',123', 123000),
+    ],
+)
+@pytest.mark.parametrize('suffix, offset', [('Z', 0), ('+05:30', 330), ('-04:30', -270)])
+def test_parse_rfc3339_fractional_seconds(fraction: str, microsecond: int, suffix: str, offset: int):
+    timestamp = f'2019-02-18T16:00:06{fraction}{suffix}'
+    expected = datetime(2019, 2, 18, 16, 0, 6, microsecond, tzinfo=timezone(timedelta(minutes=offset)))
+
+    assert parse_rfc3339(timestamp) == expected