A semantic date preset — last-30-days, this-quarter, all-time (Spec 018).

A preset is the question a user is asking ("the last 30 days"), not the answer ("Jun 29 to Jul 28"). That distinction is load-bearing: presets serialise back to their :token, so a query saved today still means "the last 30 days" when reopened next week, rather than freezing to this week's dates (ADR-011).

Fields

• :id — the canonical atom (:last_30_days), carried on Flicker.Facet.Range's :preset.
• :token — the typed/serialised form ("last-30-days").
• :label — the fallback display string. With localize present, Flicker.Facet.Format prefers CLDR's own wording (ADR-013).
• :resolve — fun(reference_date, first_day_of_week) :: {from, to}, or nil for a built-in, which resolve/3 computes from :id instead.

Why built-ins carry no function

A %Flicker.Facet{} holding presets that each closed over an anonymous function could not be a module attribute — @facets [...] fails, because anonymous functions can't be escaped into one. Since a hand-built facet registry as a module attribute is a perfectly reasonable thing to write, the built-in table stores plain data and resolve/3 dispatches on :id. A host defining its own preset may still pass a :resolve function; that preset just can't live in a module attribute.

Resolution is contextual, and takes its context as arguments

:resolve never calls Date.utc_today/0 and never reads a locale: both the reference date and the week's first day arrive as arguments. That keeps every preset a pure function — the whole table is testable at a fixed date — and it is what lets this-week mean different days in en-US (Sunday start) and en-AU (Monday start) without the preset knowing anything about locales.

first_day_of_week is 1 for Monday through 7 for Sunday, matching Date.day_of_week/1. Without localize, callers pass 1 (Monday), which is the ISO 8601 default.