---
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: 1525
product: Flux
version: v0
---

# truncateTimeColumn() function

-   Flux 0.37.0+
-   View 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/)