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## `duration()`

This function computes the number of milliseconds in a certain fixed time period. It is used to make timestamp comparisons easier, more readable and less error-prone.

Parameter | Type | Required | Default Value | Description
--- | --- | --- | --- | ---
`as` | string | optional[a] | `_duration` | The name of the output field.
`duration`[b] | string | required |  | The time duration specification. It is defined as a Relative Time Syntax such as `5m` or `2d`.
[a] Optional parameters use their default value unless explicitly set. [b] The parameter name `duration` can be omitted.

Hide omitted argument names for this function

Show omitted argument names for this function

> Omitted Argument Names

> The argument name for `duration` can be omitted; the following forms of this function are equivalent:

> logscale Syntax

>     duration("value")

> and:

> logscale Syntax

>     duration(duration="value")

> These examples show basic structure only.

The field selected by the `as` argument returns the number of milliseconds in the duration specified by the `duration` argument. The `duration` argument follows the same syntax and semantics as the duration specification mini-language used elsewhere in the system. For more information on time duration, see Relative Time Syntax.

Important

### Anchored time units not supported

You cannot use Calendar-Based Units and Anchoring to Specific Time Units to define the span length in the `duration()` function.

### `duration()` Examples

Click + next to an example below to get the full details.

#### Compare Two Timestamps

Measure time differences between events using the `duration()` function

##### Query

logscale

    diff := endTime - startTime
    | test(diff > duration("5m"))

##### Introduction

In this example, the `duration()` function is used to compute a simple value to use in a comparison. The input data contains the startTime and endTime for an operation, to determine whether the difference between the two exceeds a duration of 5 minutes.

##### Step-by-Step

1. Starting with the source repository events.

2. logscale

       diff := endTime - startTime

   Determines the difference between the endTime and startTime; the fields should be in milliseconds (as they would be for an epoch or timestamp).

3. logscale

       | test(diff > duration("5m"))

   Use the `test()` function to determine if the computed difference is greater than a duration of 5 minutes. In this case, `duration()` returns 300,000.

4. Event Result set.

##### Summary and Results

The `duration()` functions supports a more convenient, and human-readable, method of defining a duration without needing to explicitly calculate the comparison. This is particularly useful when using parameters on a dashboard.

#### Narrow the Search Interval

Filter events by relative time periods using the `duration()` function

##### Query

logscale

    test(@timestamp > now() - duration("2d"))

##### Introduction

When searching across a range of timestamps, the ability to limit the search to a more specific range using a relative duration can limit the output. To achieve this with the search, make use of `duration()` with a relative time, for example `2d` for two days and use this to compare against the current time and @timestamp of the event.

##### Step-by-Step

1. Starting with the source repository events.

2. logscale

       test(@timestamp > now() - duration("2d"))

   Creates a value based on a duration of `2d` (two days). This returns a value in milliseconds (`2 * 24 * 60 * 60 * 1000`). By subtracting the value from `now()` the value is two days ago from the time the event is executed. Then the value is compared to the @timestamp to filter the events.

3. Event Result set.

##### Summary and Results

The result is syntactically equivalent to:

logscale

    test(@timestamp > now() - 172800000)

As the value is in a human-readable and relative time syntax, the value can be used in dashboards and user-selected parameters.

#### Enter search term