Handle qcodes timestamp timezone format change and render timestamps in local time

plottr/data/qcodes_dataset.py

@@ -47,18 +47,28 @@ def _get_names_of_standalone_parameters(paramspecs: List['ParamSpec']
 def _split_timestamp(ts: Optional[str]) -> Tuple[str, str]:
     """Split a qcodes timestamp string into (date, time) components.
 
-    Uses datetime parsing instead of string slicing for robustness.
+    Uses datetime parsing instead of string slicing for robustness. This
+    handles both the legacy qcodes timestamp format (``"YYYY-MM-DD HH:MM:SS"``)
+    and the newer one that includes the UTC offset of the local timezone
+    (``"YYYY-MM-DD HH:MM:SS%z"``, e.g. ``"2026-07-31 10:27:25+0200"``).
 
-    :param ts: timestamp string as returned by ``ds.run_timestamp()``
-        (typically ``"YYYY-MM-DD HH:MM:SS"``), or None.
+    Timezone-aware timestamps are converted to the local timezone of the
+    machine running plottr before formatting, so the rendered date and time
+    always reflect the local (PC) timezone. The UTC offset itself is dropped
+    from the returned components.
+
+    :param ts: timestamp string as returned by ``ds.run_timestamp()``, or None.
     :returns: (date_str, time_str) or ('', '') if ts is None or unparsable.
     """
     if ts is None:
         return '', ''
     try:
         dt = datetime.fromisoformat(ts)
+        if dt.tzinfo is not None:
+            # Render in the local timezone of the machine running plottr.
+            dt = dt.astimezone()
         return dt.strftime('%Y-%m-%d'), dt.strftime('%H:%M:%S')
-    except (ValueError, TypeError):
+    except (ValueError, TypeError, OSError, OverflowError):
         return '', ''
 
 

test/pytest/test_qcodes_data.py

@@ -1,3 +1,6 @@
+import datetime
+import time
+
 import numpy as np
 import pytest
 from packaging import version
@@ -13,7 +16,8 @@
     get_ds_structure,
     get_ds_info,
     get_runs_from_db,
-    ds_to_datadict)
+    ds_to_datadict,
+    _split_timestamp)
 
 
 @pytest.fixture(scope='function')
@@ -180,6 +184,63 @@ def test_get_ds_structure(experiment):
     assert structure == expected_structure
 
 
+def test_split_timestamp_naive():
+    # The legacy qcodes timestamp format has no timezone information and is
+    # returned as-is (split into date and time). Expected values are hard-coded
+    # so this does not depend on the helper's own logic.
+    assert _split_timestamp("2026-07-31 10:27:25") == ("2026-07-31", "10:27:25")
+
+
+def test_split_timestamp_none_and_invalid():
+    assert _split_timestamp(None) == ("", "")
+    assert _split_timestamp("") == ("", "")
+    assert _split_timestamp("not a timestamp") == ("", "")
+
+
+def test_split_timestamp_timezone_aware_rendered_in_local_time():
+    # The new qcodes timestamp format includes the UTC offset. Such timestamps
+    # must be converted to the local timezone of the machine before being split.
+    # We compute the expected local date/time independently from the helper:
+    # take a fixed absolute instant, convert it to local wall-clock time via
+    # ``datetime.fromtimestamp`` (a different code path than the helper), and
+    # verify the helper agrees for the same instant given in different offsets.
+    utc_instant = datetime.datetime(2026, 7, 31, 8, 27, 25,
+                                    tzinfo=datetime.timezone.utc)
+    local = datetime.datetime.fromtimestamp(utc_instant.timestamp())
+    expected = (local.strftime("%Y-%m-%d"), local.strftime("%H:%M:%S"))
+
+    # Same instant expressed as UTC (+00:00) and as +02:00.
+    assert _split_timestamp("2026-07-31 08:27:25+00:00") == expected
+    assert _split_timestamp("2026-07-31 10:27:25+02:00") == expected
+    # qcodes renders the offset without a colon (e.g. "+0000"); ensure that
+    # format is handled too.
+    assert _split_timestamp("2026-07-31 08:27:25+0000") == expected
+
+
+def test_split_timestamp_timezone_aware_crosses_date_boundary(monkeypatch):
+    # Converting to local time can push the timestamp onto a different
+    # calendar date than the one written in the input string. The local
+    # timezone is pinned explicitly so the boundary crossing is guaranteed
+    # regardless of the host machine's own timezone. Expected values are
+    # again derived independently via ``datetime.fromtimestamp``.
+    if not hasattr(time, "tzset"):
+        pytest.skip("time.tzset is not available on this platform")
+
+    monkeypatch.setenv("TZ", "Europe/Berlin")
+    time.tzset()
+    try:
+        utc_instant = datetime.datetime(2026, 7, 31, 23, 30, 0,
+                                        tzinfo=datetime.timezone.utc)
+        local = datetime.datetime.fromtimestamp(utc_instant.timestamp())
+        expected = (local.strftime("%Y-%m-%d"), local.strftime("%H:%M:%S"))
+
+        # Same instant, expressed with a +02:00 offset, which shifts the
+        # calendar date in the input string to the next day.
+        assert _split_timestamp("2026-08-01 01:30:00+02:00") == expected
+    finally:
+        time.tzset()
+
+
 def test_get_ds_info(experiment):
     N = 5
 
@@ -201,17 +262,20 @@ def test_get_ds_info(experiment):
 
     # timestamps are difficult to test for, so we will cheat here and
     # instead of hard-coding timestamps we will just get them from the dataset
-    # The same applies to the guid as it contains the timestamp
-    started_ts = dataset.run_timestamp()
-    completed_ts = dataset.completed_timestamp()
+    # The same applies to the guid as it contains the timestamp.
+    # To avoid testing ``get_ds_info`` against the very helper it uses
+    # (``_split_timestamp``), we derive the expected local date/time
+    # independently from the raw unix timestamps exposed by qcodes.
+    started = datetime.datetime.fromtimestamp(dataset.run_timestamp_raw)
+    completed = datetime.datetime.fromtimestamp(dataset.completed_timestamp_raw)
 
     expected_ds_info = {
         'experiment': '2d_softsweep',
         'sample': 'no sample',
-        'completed_date': completed_ts[:10],
-        'completed_time': completed_ts[11:],
-        'started_date': started_ts[:10],
-        'started_time': started_ts[11:],
+        'completed_date': completed.strftime('%Y-%m-%d'),
+        'completed_time': completed.strftime('%H:%M:%S'),
+        'started_date': started.strftime('%Y-%m-%d'),
+        'started_time': started.strftime('%H:%M:%S'),
         'name': 'results',
         'structure': None,
         'records': 0,

test_requirements.txt

@@ -2,7 +2,11 @@ qcodes
 pytest
 pytest-qt
 hypothesis
-mypy==2.3.1
+# mypy >=2.2.0 crashes with an INTERNAL ERROR while following imports into
+# qcodes' data_set_protocol.py (verified up to 2.3.1, the latest release as
+# of writing). Pinned to 2.1.0, the newest version that doesn't crash; bump
+# once upstream fixes this (see https://github.com/python/mypy/issues/21741).
+mypy==2.1.0
 PySide6-stubs
 pandas-stubs
 watchdog