# `Duration`

A length of time, exact to the millisecond, written `PT1H30M`.

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

## Make one

`text.parse(raw, as: Duration)` reads one from its text; text that isn't one at all fails `malformed`, such as `5 minutes`, `P` or `PT`.

This operation gives one: `temporal.between`.

## 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 |
|---|---|
| `PT5M` | `"PT5M"` |
| `PT1H30M` | `"PT1H30M"` |
| `PT26H` | `"PT26H"` |

It is stored in one column named for the field, of type `bigint`. `PT1H30M` is stored as `5400000`.

## Shown to people

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

With `locale: Locale.en_gb`:

| Value | Shown |
|---|---|
| `PT5M` | `5 minutes` |
| `PT1H30M` | `1 hour, 30 minutes` |
| `PT26H` | `1 day, 2 hours` |

## Operations

- `temporal.between(start: Instant, end: Instant) -> Duration`: How long from `start` to `end`: `end - start`.

Like every standard type, it also 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.