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

The `~o` sigil: an ISO 8601 text read at compile time.

In an expression, `~o"2026-06-15"` is the `%Tempo{}` the text names, read
once when the module compiles, so a text that cannot be read is a compile
error. A duration text is a `%Tempo.Duration{}`.

In a pattern, the sigil is a structural match on the form the text names.
A value matches every value whose units *begin with* the units written,
so `~o"2026-06"` matches `~o"2026-06-15"` and `~o"2026-06-15T10"`, and no
other field is constrained: a Gregorian-looking sigil matches a value of
another calendar. An interval, a set or a recurrence matches that form
exactly.

    iex> import Tempo.Sigils
    iex> match?(~o"2026-06", ~o"2026-06-15")
    true
    iex> match?(~o"2026-06", ~o"2026-07-15")
    false

# `sigil_o`
*macro* 

Reads an ISO 8601 text into an expression at compile time, or into a
pattern that matches one.

### Arguments

* The sigil's text, an ISO 8601 text as Tempo reads it. It is a literal:
  a text with an interpolation is refused, since it would be read at
  compile time.

* `modifiers`, which `~o` takes none of.

### Returns

* The expression or the duration the text reads to, built when the code
  is compiled, or a pattern matching it where the sigil is in a pattern.
  A text that does not read is a compile error naming why.

### Examples

    iex> ~o"2026-06-15"
    Tempo.from_iso8601!("2026-06-15")

    iex> ~o"P1Y2M"
    Tempo.Duration.new!(year: 1, month: 2)

---

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