fix #1145 - normalize git commit timestamp to utc

Author: RonnyPfannschmidt

CHANGELOG.md

@@ -15,6 +15,7 @@
 
 ### Fixed
 
+- fix #1145: ensure GitWorkdir.get_head_date returns consistent UTC dates regardless of local timezone
 - reintroduce Python 3.9 entrypoints shim for compatibility
 - fix #1136: update customizing.md to fix missing import
 

src/setuptools_scm/_run_cmd.py

@@ -81,6 +81,16 @@ def parse_success(
             return parse(self.stdout)
 
 
+KEEP_GIT_ENV = (
+    "GIT_CEILING_DIRECTORIES",
+    "GIT_EXEC_PATH",
+    "GIT_SSH",
+    "GIT_SSH_COMMAND",
+    "GIT_AUTHOR_DATE",
+    "GIT_COMMITTER_DATE",
+)
+
+
 def no_git_env(env: Mapping[str, str]) -> dict[str, str]:
     # adapted from pre-commit
     # Too many bugs dealing with environment variables and GIT:
@@ -95,11 +105,7 @@ def no_git_env(env: Mapping[str, str]) -> dict[str, str]:
         if k.startswith("GIT_"):
             log.debug("%s: %s", k, v)
     return {
-        k: v
-        for k, v in env.items()
-        if not k.startswith("GIT_")
-        or k
-        in ("GIT_CEILING_DIRECTORIES", "GIT_EXEC_PATH", "GIT_SSH", "GIT_SSH_COMMAND")
+        k: v for k, v in env.items() if not k.startswith("GIT_") or k in KEEP_GIT_ENV
     }
 
 

src/setuptools_scm/git.py

@@ -123,7 +123,13 @@ def parse_timestamp(timestamp_text: str) -> date | None:
                 return None
             if sys.version_info < (3, 11) and timestamp_text.endswith("Z"):
                 timestamp_text = timestamp_text[:-1] + "+00:00"
-            return datetime.fromisoformat(timestamp_text).date()
+
+            # Convert to UTC to ensure consistent date regardless of local timezone
+            dt = datetime.fromisoformat(timestamp_text)
+            log.debug("dt: %s", dt)
+            dt_utc = dt.astimezone(timezone.utc).date()
+            log.debug("dt utc: %s", dt_utc)
+            return dt_utc
 
         res = run_git(
             [

testing/test_git.py

@@ -515,6 +515,36 @@ def test_git_getdate_git_2_45_0_plus(
         assert git_wd.get_head_date() == date(2024, 4, 30)
 
 
+def test_git_getdate_timezone_consistency(
+    wd: WorkDir, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    """Test that get_head_date returns consistent UTC dates regardless of local timezone.
+
+    This test forces a git commit with a timestamp that represents a time
+    after midnight in a positive timezone offset but still the previous day in UTC.
+    This is the exact scenario that was causing test failures in issue #1145.
+    """
+    # Create a timestamp that's problematic:
+    # - In Europe/Berlin (UTC+2): 2025-06-12 00:30:00 (June 12th)
+    # - In UTC: 2025-06-11 22:30:00 (June 11th)
+    problematic_timestamp = "2025-06-12T00:30:00+02:00"
+
+    # Force git to use this specific timestamp for the commit
+    monkeypatch.setenv("GIT_AUTHOR_DATE", problematic_timestamp)
+    monkeypatch.setenv("GIT_COMMITTER_DATE", problematic_timestamp)
+
+    wd.commit_testfile()
+
+    git_wd = git.GitWorkdir(wd.cwd)
+    result_date = git_wd.get_head_date()
+
+    # The correct behavior is to return the UTC date (2025-06-11)
+    # If the bug is present, it would return the timezone-local date (2025-06-12)
+    expected_utc_date = date(2025, 6, 11)
+
+    assert result_date == expected_utc_date
+
+
 @pytest.fixture
 def signed_commit_wd(monkeypatch: pytest.MonkeyPatch, wd: WorkDir) -> WorkDir:
     if not has_command("gpg", args=["--version"], warn=False):