diff --git a/snuba/util.py b/snuba/util.py
index 6d6b73f27d..0a08b8611d 100644
--- a/snuba/util.py
+++ b/snuba/util.py
@@ -113,7 +113,7 @@ def get_re(format: Sequence[PartSegment]) -> Pattern[Any]:
     if date_str and retention_days:
         return Part(
             part_str,
-            datetime.strptime(date_str, "%Y-%m-%d").astimezone(UTC),
+            datetime.strptime(date_str, "%Y-%m-%d").replace(tzinfo=UTC),
             int(retention_days),
         )
 
diff --git a/tests/test_util.py b/tests/test_util.py
index 08f48076b3..b0ae674c79 100644
--- a/tests/test_util.py
+++ b/tests/test_util.py
@@ -1,4 +1,11 @@
+import time
+from collections.abc import Generator
+from datetime import UTC, datetime
+
+import pytest
+
 from snuba.clickhouse.escaping import escape_alias, escape_identifier
+from snuba.util import PartSegment, decode_part_str
 
 
 def test_escape_identifier() -> None:
@@ -21,3 +28,21 @@ def test_escape_alias() -> None:
     assert escape_alias("foo") == "foo"
     assert escape_alias("foo.bar") == "`foo.bar`"
     assert escape_alias("foo:bar") == "`foo:bar`"
+
+
+@pytest.fixture
+def local_timezone(monkeypatch: pytest.MonkeyPatch) -> Generator[None]:
+    # A zone east of UTC, where local midnight falls on the previous UTC day.
+    with monkeypatch.context() as m:
+        m.setenv("TZ", "Asia/Tokyo")
+        time.tzset()
+        yield
+    time.tzset()
+
+
+@pytest.mark.usefixtures("local_timezone")
+def test_decode_part_str_ignores_local_timezone() -> None:
+    part = decode_part_str("(90,'2026-10-12')", [PartSegment.RETENTION_DAYS, PartSegment.DATE])
+    assert part.date == datetime(2026, 10, 12, tzinfo=UTC)
+    assert part.date.weekday() == 0
+    assert part.retention_days == 90