---
title: truncateTimeColumn() function
description: truncateTimeColumn() truncates all input time values in the _time to a specified unit.
url: https://docs.influxdata.com/flux/v0/stdlib/universe/truncatetimecolumn/
estimated_tokens: 944
product: Flux
version: v0
publisher: InfluxData
canonical: https://docs.influxdata.com/flux/v0/stdlib/universe/truncatetimecolumn/
date: '2024-04-08T16:01:02-06:00'
lastmod: '2024-04-08T16:01:02-06:00'
---

* Flux 0.37.0+

InfluxDB support

`truncateTimeColumn()` truncates all input time values in the `_time` to a
specified unit.

#### Truncate to weeks

When truncating a time value to the week (`1w`), weeks are determined using the**Unix epoch (1970-01-01T00:00:00Z UTC)**. The Unix epoch was on a Thursday,
so all calculated weeks begin on Thursday.

##### Function type signature

```js
(<-tables: stream[{B with _time: C}], unit: duration, ?timeColumn: A) => stream[{B with _time: C, _time: time}] where C: Timeable
```

For more information, see [Function type signatures](/flux/v0/function-type-signatures/).

## Parameters

### unit

(Required)
Unit of time to truncate to.

**Example units:**

* 1ns (nanosecond)
* 1us (microsecond)
* 1ms (millisecond)
* 1s (second)
* 1m (minute)
* 1h (hour)
* 1d (day)
* 1w (week)
* 1mo (month)
* 1y (year)

### timeColumn

Time column to truncate. Default is `_time`.

**Note:** Currently, assigning a custom value to this parameter will have
no effect.

### tables

Input data. Default is piped-forward data (`<-`).

## Examples

### Truncate all time values to the minute

```js
import "sampledata"

sampledata.int()
    |> truncateTimeColumn(unit: 1m)
```

[](#view-example-input-and-output)

View example input and output

#### Input data

|       \_time       |\_value|\*tag|
|--------------------|-------|-----|
|2021-01-01T00:00:00Z|  \-2  | t1  |
|2021-01-01T00:00:10Z|  10   | t1  |
|2021-01-01T00:00:20Z|   7   | t1  |
|2021-01-01T00:00:30Z|  17   | t1  |
|2021-01-01T00:00:40Z|  15   | t1  |
|2021-01-01T00:00:50Z|   4   | t1  |

|       \_time       |\_value|\*tag|
|--------------------|-------|-----|
|2021-01-01T00:00:00Z|  19   | t2  |
|2021-01-01T00:00:10Z|   4   | t2  |
|2021-01-01T00:00:20Z|  \-3  | t2  |
|2021-01-01T00:00:30Z|  19   | t2  |
|2021-01-01T00:00:40Z|  13   | t2  |
|2021-01-01T00:00:50Z|   1   | t2  |

#### Output data

|       \_time       |\_value|\*tag|
|--------------------|-------|-----|
|2021-01-01T00:00:00Z|  \-2  | t1  |
|2021-01-01T00:00:00Z|  10   | t1  |
|2021-01-01T00:00:00Z|   7   | t1  |
|2021-01-01T00:00:00Z|  17   | t1  |
|2021-01-01T00:00:00Z|  15   | t1  |
|2021-01-01T00:00:00Z|   4   | t1  |

|       \_time       |\_value|\*tag|
|--------------------|-------|-----|
|2021-01-01T00:00:00Z|  19   | t2  |
|2021-01-01T00:00:00Z|   4   | t2  |
|2021-01-01T00:00:00Z|  \-3  | t2  |
|2021-01-01T00:00:00Z|  19   | t2  |
|2021-01-01T00:00:00Z|  13   | t2  |
|2021-01-01T00:00:00Z|   1   | t2  |

#### Related

* [date.truncate() function](/flux/v0/stdlib/date/truncate/)

[transformations](/flux/v0/tags/transformations/)[date/time](/flux/v0/tags/date/time/)
| _time | _value | *tag |
| --- | --- | --- |
| _time | _value | *tag |
| 2021-01-01T00:00:00Z | -2 | t1 |
| 2021-01-01T00:00:10Z | 10 | t1 |
| 2021-01-01T00:00:20Z | 7 | t1 |
| 2021-01-01T00:00:30Z | 17 | t1 |
| 2021-01-01T00:00:40Z | 15 | t1 |
| 2021-01-01T00:00:50Z | 4 | t1 |

| _time | _value | *tag |
| --- | --- | --- |
| _time | _value | *tag |
| 2021-01-01T00:00:00Z | 19 | t2 |
| 2021-01-01T00:00:10Z | 4 | t2 |
| 2021-01-01T00:00:20Z | -3 | t2 |
| 2021-01-01T00:00:30Z | 19 | t2 |
| 2021-01-01T00:00:40Z | 13 | t2 |
| 2021-01-01T00:00:50Z | 1 | t2 |

| _time | _value | *tag |
| --- | --- | --- |
| _time | _value | *tag |
| 2021-01-01T00:00:00Z | -2 | t1 |
| 2021-01-01T00:00:00Z | 10 | t1 |
| 2021-01-01T00:00:00Z | 7 | t1 |
| 2021-01-01T00:00:00Z | 17 | t1 |
| 2021-01-01T00:00:00Z | 15 | t1 |
| 2021-01-01T00:00:00Z | 4 | t1 |

| _time | _value | *tag |
| --- | --- | --- |
| _time | _value | *tag |
| 2021-01-01T00:00:00Z | 19 | t2 |
| 2021-01-01T00:00:00Z | 4 | t2 |
| 2021-01-01T00:00:00Z | -3 | t2 |
| 2021-01-01T00:00:00Z | 19 | t2 |
| 2021-01-01T00:00:00Z | 13 | t2 |
| 2021-01-01T00:00:00Z | 1 | t2 |