# `Tempo.ConversionError`
[🔗](https://github.com/elixir-tempo/tempo/blob/v2.1.0/lib/tempo/exception/conversion_error.ex#L1)

An expression that cannot be given the spans asked of it, with the
reason: a duration has no place on the time line, a one-of set has
readings and no spans, a value with no year needs one, a sequence with
no end needs a `:within` window, or more values were asked for at once
than the application's `:max_values_at_once` allows (10,000 unless it is set).

# `reason`

```elixir
@type reason() ::
  :bare_duration
  | :one_of
  | :needs_a_year
  | :unbounded
  | :open
  | :too_many_values
  | :season
  | {:no_hemisphere, atom()}
  | {:season_moved, Tempo.Duration.t()}
  | :selection
  | :exclusion
  | :repeat_rule
  | :no_such_value
  | :group
  | :several
  | :conditions
  | :not_an_expression
  | :not_an_elixir_value
  | :not_a_duration
  | :nothing_finer
  | {:no_walk, atom()}
  | :not_an_interval
  | {:not_written_in, :season | :traditional_month}
  | term()
```

# `t`

```elixir
@type t() :: %Tempo.ConversionError{
  __exception__: term(),
  reason: reason(),
  value: term()
}
```

---

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