# `Calendrical.NotDefinedError`

Exception returned when a calendar does not define what was asked of
it: weeks in a calendar without them, a cycle of years in a calendar
whose years do not repeat, or one count of days for a month whose days
change from year to year.

### Fields

* `:calendar` — the calendar module that was asked.

* `:question` — what was asked, such as `:week`, `:quarter`,
  `:years_in_cycle` or `:days_in_month`.

* `:value` — the value it was asked about, or `nil`.

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*Consult [api-reference.md](api-reference.md) for complete listing*