# Period open

`period_open`

The opening price of the current day, week or month.

## Inputs

| Name | Type | Default | Range |
| --- | --- | --- | --- |
| period | choice | D |  |
| day_boundary | text | 17:00 America/New_York |  |

## Outputs

| Name | Kind |
| --- | --- |
| period_open | value |

Warm-up: 0 bars (0 at the defaults).

Repaints: No.

## Formula

A trading day starts at day_boundary; period D, W or M is defined as for prior levels.

period_open is the open of the first bar of the current period, shown on every bar of that period. A period already under way at the first bar of the data has no value.