# `IsoWeek`

A week of an ISO 8601 week-numbering year, written `2026-W43`: `week` from 1 to 52, or 53 in a year that has one.

[Time and calendar](types.md#time-and-calendar); ordered; since Jadpo 0.1.0.

## Make one

Build one from its fields, `IsoWeek { year: ...  week: ... }`.

`text.parse(raw, as: IsoWeek)` reads one from its text; text that isn't one at all fails `malformed`, such as `2027-W53`, `2026-W54` or `2026-W00`.

Its parts keep these rules; a value that breaks one fails with the rule's name:

- `week_in_year`: `week is 53 only in a year with 53 ISO weeks`

## Fields

| Field | Type |
|---|---|
| `year` | `Int` |
| `week` | `Int` |

## Text, JSON and storage

`text.from` writes its canonical text, the one form `text.parse` reads back. JSON sends its canonical text as a string.

| Text | JSON |
|---|---|
| `2026-W01` | `"2026-W01"` |
| `2026-W53` | `"2026-W53"` |

It is stored in 2 columns, each named for the field, `_` and its suffix. This is `2026-W53`:

| Column | Type | Holds |
|---|---|---|
| `<field>_year` | `smallint` | `2026` |
| `<field>_week` | `smallint` | `53` |

## Shown to people

`text.format(value, locale:)` shows it to people in their locale.

With `locale: Locale.en_gb`:

| Value | Shown |
|---|---|
| `2026-W01` | `2026-W01` |
| `2026-W53` | `2026-W53` |

## Operations

It has the contract's own operations: `text.parse`, `text.from`, `text.format`, `json.read`, `json.write` and `==`. It is ordered, so `<` and sorting take it. [Every standard type meets one contract](../topics/every-standard-type-meets-one-contract.md) says how they work.