---
title: time.units
summary: null
url: >-
  https://www.fastly.com/documentation/reference/vcl/functions/date-and-time/time-units
---

```
STRING time.units(STRING unit, TIME time)
```

**Available in:** all subroutines

Returns a string representation of the given TIME typed time value expressed to
the resolution specified by the unit.

## Parameters

- `unit` - A string of one of the four possible unit types - `s`, `ms`, `us`,
  `ns`.
- `time` - A time value parameter of type TIME.

## Return Value

The return value will be of type STRING, being the text-based representation of
the given time value formatted according to the unit type as specified by the
following criteria:

| Unit | Description                                                         |
| ---: | :------------------------------------------------------------------ |
|  `s` | Whole seconds only with no decimal point                            |
| `ms` | Whole seconds followed by a decimal point with three decimal places |
| `us` | Whole seconds followed by a decimal point with six decimal places   |
| `ns` | Whole seconds followed by a decimal point with nine decimal places  |

## Errors

If the `unit` argument is not a valid unit string,
then `fastly.error` will be set to `EINVAL`.

## Example

```vcl
set resp.http.X-Request-Start-Time = time.units("s", time.start);
```