---
title: state_periods() | Tiger Data Docs
description: Get the time periods corresponding to a given state from a state aggregate
---

Since [1.15.0](https://github.com/timescale/timescaledb-toolkit/releases/tag/1.15.0)

List the periods when the system is in a specific state from a state aggregate. Periods are defined by the start time and end time.

If you have multiple state aggregates and need to interpolate the state across interval boundaries, use [`interpolated_state_periods`](/docs/reference/toolkit/state-tracking/state_agg/interpolated_state_periods/index.md).

## Samples

Create a state aggregate and list all periods corresponding to the state `OK`.

```
SELECT start_time, end_time FROM state_periods(
  (SELECT state_agg(ts, state) FROM states_test),
  'OK',
);
```

Returns:

```
       start_time       |        end_time
------------------------+------------------------
 2020-01-01 00:00:11+00 | 2020-01-01 00:01:00+00
 2020-01-01 00:01:03+00 | 2020-01-01 00:02:00+00
```

## Arguments

The syntax is:

```
state_periods(
    agg StateAgg,
    state [TEXT | BIGINT]
) RETURNS (TIMESTAMPTZ, TIMESTAMPTZ)
```

| Name  | Type     | Default | Required | Description                                                                                                        |
| ----- | -------- | ------- | -------- | ------------------------------------------------------------------------------------------------------------------ |
| agg   | StateAgg | -       | ✔        | A state aggregate created using [`state_agg`](/docs/reference/toolkit/state-tracking/state_agg/state_agg/index.md) |
| state | TEXT     | BIGINT  | -        | ✔                                                                                                                  |

## Returns

| Column      | Type        | Description                                 |
| ----------- | ----------- | ------------------------------------------- |
| start\_time | TIMESTAMPTZ | The time when the state started (inclusive) |
| end\_time   | TIMESTAMPTZ | The time when the state ended (exclusive)   |