[Bug]: date of birth date time round trip

[bendichter]

What happened?

After adding date as an allowable type for Subject.date_of_birth:

{'name': 'date_of_birth', 'type': (datetime, date), 'default': None,

a Subject date_of_birth can be set with a date object. This can be written to an NWB file which stores the date correctly. However, on read, the date_of_birth is converted to a datetime.

Steps to Reproduce

from pynwb.file import Subject
from pynwb import NWBHDF5IO
from datetime import date, datetime
from pynwb.testing.mock.file import mock_NWBFile
from h5py import File

# A Subject date_of_birth can be set with a date object
subject = Subject(subject_id="001", date_of_birth=date(2022, 1, 1))
assert isinstance(subject.date_of_birth, date)
print("Value in Subject object:", subject.date_of_birth)

# This can be written to an NWB file
nwbfile = mock_NWBFile(subject=subject)

with NWBHDF5IO("test_dob_date", "w") as io:
    io.write(nwbfile)
    
# The resulting NWB file stores the date correctly
with File("test_dob_date") as file:
    print("Value in NWB file:", file["general/subject/date_of_birth"][()])
    
    
# However, on read, the date of birth is converted to a datetime
with NWBHDF5IO("test_dob_date", "r") as io:
    read_nwbfile = io.read()
    
print("Value in read NWBFile object:", read_nwbfile.subject.date_of_birth)

assert isinstance(read_nwbfile.subject.date_of_birth, datetime)

assert read_nwbfile.subject.date_of_birth == nwbfile.subject.date_of_birth

Traceback

No response

Operating System

macOS

Python Executable

Conda

Python Version

3.9

Package Versions

No response

Code of Conduct

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• Have you ensured this bug was not already reported?

[bendichter]

I think this escaped me in hdmf-dev/hdmf#874 because a datetime isa date:

from datetime import date, datetime

isinstance(datetime.now(), date)  # this is True, which I did not expect.

[bendichter]

I'm not able to find in HDMF where the iso date format string is mapped to the datetime type. @rly , do you know where this would be?