This comment https://github.com/cqframework/cql-tests/blob/main/tests/cql/CqlTypesTest.xml#L209 incorrectly suggests that @T23:59:59.10000 means "23:59:59 + 10000 milliseconds" while it should be intepreted as "23:59:59 + 0.10000 seconds".
According to the FHIRPath spec:
The Time literal uses a subset of ISO8601.
Also:
Implementations MUST support at least 3 digits (milliseconds); support for additional digits is optional.