isISO8601Date rejects valid ISO 8601 timestamps, including the form the NWB schema recommends #329

AQNWB::isISO8601Date (src/Utils.hpp:200) requires a fractional seconds part and a numeric ±HH:MM offset. Both are optional in ISO 8601.

const std::string iso8601Pattern =
    R"(^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}\.\d+[+-]\d{2}:\d{2}$)";

This has stayed hidden because getCurrentTime() (src/Utils.hpp:174) emits exactly the one accepted shape, so AqNWB generated values always pass. It bites on caller supplied values, at NWBFile.cpp:81 (sessionStartTime), NWBFile.cpp:86 (timestampsReferenceTime), and Subject.cpp:73 (date_of_birth).

Rejected, all valid ISO 8601:

• 2024-01-15T00:00:00Z, the UTC designator
• 2024-01-15T00:00:00.000Z, the form the NWB schema's isodatetime doc text describes ("Dates stored in UTC end in "Z" with no timezone offset. Date accuracy is up to milliseconds.")
• 2024-01-15T00:00:00+00:00, what datetime.isoformat() produces for a whole second
• 2024-01-15T00:00:00.123+0000, basic format offset

The tests assert the wrong contract

Four assertions in tests/testUtilsFunctions.cpp:21-36 classify valid ISO 8601 as invalid, with comments that do not hold. Fractional seconds are optional, +0200 and -0800 are valid basic format offsets, and Z specifies UTC rather than omitting it.

REQUIRE_FALSE(AQNWB::isISO8601Date("2018-09-28T14:43:54+02:00"));     // Missing fractional seconds
REQUIRE_FALSE(AQNWB::isISO8601Date("2018-09-28T14:43:54.123+0200"));  // Missing colon in timezone
REQUIRE_FALSE(AQNWB::isISO8601Date("2018-09-28T14:43:54.123Z"));      // Missing timezone offset
REQUIRE_FALSE(AQNWB::isISO8601Date("2018-09-28T14:43:54.123-0800"));  // Incorrect timezone format

The other three assertions in that section are correct and should stay: a space in place of T, a string with no timezone information, and free text. Requiring an explicit timezone is a real NWB best practice.

Proposed change

const std::string iso8601Pattern =
    R"(^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}(\.\d+)?(Z|[+-]\d{2}:?\d{2})$)";

Checked against every string above and every string the current tests accept. It still rejects the hour only offset (+02), which ISO 8601 permits but nothing in the NWB ecosystem emits.

Relatedly, the function name says Date while it validates a datetime. Rename to isISO8601DateTime?

Acceptance criteria

• The four forms listed above are accepted, and getCurrentTime() output still validates.
• Strings with no timezone designator, with a space in place of T, and free text remain rejected.
• tests/testUtilsFunctions.cpp moves the four mislabeled cases to the valid section and drops the incorrect comments.

Out of scope: a bare date such as 2024-01-15 stays rejected, since the NWB dtype for all three fields is isodatetime.

Generated by Claude Code and reviewed by me.