FIX: ctf data can sometimes have no date time.

doc/changes/latest.inc

@@ -142,6 +142,8 @@ Bugs
 
 - Fix bug in :func:`mne.io.read_raw_ctf` on Windows where large files could not be read (:gh:`10866` by `Eric Larson`_)
 
+- Fix bug in :func:`mne.io.read_raw_ctf` where invalid measurement dates were not handled properly (:gh:`10957` by `Jean-Remi King`_ and `Eric Larson`_)
+
 - Rendering issues with recent MESA releases can be avoided by setting the new environment variable``MNE_3D_OPTION_MULTI_SAMPLES=1`` or using :func:`mne.viz.set_3d_options` (:gh:`10513` by `Eric Larson`_)
 
 - Fix behavior for the ``pyvista`` 3D renderer's ``quiver3D`` function so that default arguments plot a glyph in ``arrow`` mode (:gh:`10493` by `Alex Rockhill`_)

mne/io/ctf/info.py

@@ -73,6 +73,12 @@ def _pick_isotrak_and_hpi_coils(res4, coils, t):
 
 def _convert_time(date_str, time_str):
     """Convert date and time strings to float time."""
+    if date_str == time_str == '':
+        date_str = '01/01/1970'
+        time_str = '00:00:00'
+        logger.info('No date or time found, setting to the start of the '
+                    'POSIX epoch (1970/01/01 midnight)')
+
     for fmt in ("%d/%m/%Y", "%d-%b-%Y", "%a, %b %d, %Y", "%Y/%m/%d"):
         try:
             date = strptime(date_str.strip(), fmt)

mne/io/ctf/tests/test_ctf.py

@@ -3,6 +3,7 @@
 # License: BSD-3-Clause
 
 import copy
+from datetime import datetime, timezone
 import os
 from os import path as op
 import shutil
@@ -13,12 +14,14 @@
 import pytest
 
 import mne
+import mne.io.ctf.info
 from mne import (pick_types, read_annotations, create_info,
                  events_from_annotations, make_forward_solution)
 from mne.transforms import apply_trans
 from mne.io import read_raw_fif, read_raw_ctf, RawArray
 from mne.io.compensator import get_current_comp
 from mne.io.ctf.constants import CTF
+from mne.io.ctf.info import _convert_time
 from mne.io.tests.test_raw import _test_raw_reader
 from mne.tests.test_annotations import _assert_annotations_equal
 from mne.utils import (_clean_names, catch_logging, _stamp_to_dt,
@@ -439,3 +442,17 @@ def test_read_ctf_mag_bad_comp(tmp_path, monkeypatch):
     monkeypatch.setattr(mne.io.ctf.ctf, '_read_res4', _bad_res4_grad_comp)
     with pytest.raises(RuntimeError, match='inconsistent compensation grade'):
         read_raw_ctf(path)
+
+
+@testing.requires_testing_data
+def test_invalid_meas_date(monkeypatch):
+    """Test handling of invalid meas_date."""
+    def _convert_time_bad(date_str, time_str):
+        return _convert_time('', '')
+    monkeypatch.setattr(mne.io.ctf.info, '_convert_time', _convert_time_bad)
+
+    with catch_logging() as log:
+        raw = read_raw_ctf(ctf_dir / ctf_fname_continuous, verbose=True)
+    log = log.getvalue()
+    assert 'No date or time found' in log
+    assert raw.info['meas_date'] == datetime.fromtimestamp(0, tz=timezone.utc)