Module errors 

Typed error enum for date construction and convention dispatch.

All failure paths return a typed Result — no panic!(), no unwrap(), no string errors. Each variant carries enough context for the caller to report precisely what was wrong and where.

A single enum covers the two failure domains the crate can produce:

• ValidationError::InvalidDate — a (year, month, day) triple does not name a real Gregorian date (e.g. 31 February, a 0 month).
• ValidationError::OutOfRange — a value is well-formed in isolation but falls outside the range a convention or calendar accepts.

It implements core::fmt::Display and core::error::Error, so it composes with ? and with dyn Error even under #![no_std].

References

• ISO 8601 (Gregorian calendar date format) — the date grammar these errors report against.

Enums

ValidationError

Error returned when an input cannot be accepted as a valid date or when a value falls outside the range a convention accepts.