---
name: "[up-time]"
area: "API"
kind: "HTML attribute"
parent: "up.fragment module"
url: "https://unpoly.com/api/up-time"
---
<nav aria-label="Unpoly docs">[All docs](https://unpoly.com/index.md) · [up.fragment module](https://unpoly.com/api/up.fragment.md)</nav>

# [up-time]

Sets the time when the fragment's underlying data was last changed.

When the fragment is reloaded, its known modification time is sent as an [`If-Modified-Since`](https://unpoly.com/api/If-Modified-Since.md) request header. The server may check the header and decide to [skip rendering](https://unpoly.com/learn/conditional-requests.md).

<nav aria-label="Guides">

- [Learn: Conditional requests](https://unpoly.com/learn/conditional-requests.md)

</nav>

## How `[up-time]` attributes are set {#how-up-time-attributes-are-set}

Unpoly will automatically set an `[up-time]` attribute when a fragment was rendered from a response with a [`Last-Modified`](https://unpoly.com/api/Last-Modified.md) header. When a fragment was rendered without such a header, Unpoly will set `[up-time=false]` to indicate that its modification time is unknown.

A large response may contain multiple fragments that are later reloaded individually and should each have their own modification time. In this case the server may also render multiple fragments with each their own `[up-time]` attribute. See [Individual versions per fragment](https://unpoly.com/learn/conditional-requests.md#fragment-versions) for an example.

---

## Modifying attributes {#attributes}

### up-time {#up-time}

(required)

The time when the element's underlying data was last changed.

The value can either be a Unix timestamp (e.g. `"1445412480"`) or an [RFC 1123](https://www.rfc-editor.org/rfc/rfc1123) time (e.g. `Wed, 21 Oct 2015 07:28:00 GMT`).

You can also set the value to `"false"` to prevent a [`If-Modified-Since`](https://unpoly.com/api/If-Modified-Since.md) request header when reloading this fragment.

Type: string