---
title: "What is the 'asAt' timestamp?"
slug: "what-is-the-asat-timestamp"
updated: 2024-08-19T09:37:24Z
published: 2024-08-19T09:37:24Z
canonical: "support.lusid.com/what-is-the-asat-timestamp"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://support.lusid.com/llms.txt
> Use this file to discover all available pages before exploring further.

# What is the 'asAt' timestamp?

For [bitemporal data](/v1/docs/what-is-bitemporal-data), the `asAt` timestamp reflects the point in time at which a data item is saved into LUSID. [Find out about the effectiveAt timestamp](/v1/docs/what-are-the-effectiveat-and-effectivefrom-timestamps).

An `asAt` timestamp is determined internally by LUSID and cannot be updated by the user. As such, methods which update data in LUSID do not take an `asAt` parameter.

All `List*` and `Get*` APIs include a parameter for specifying the `asAt` timestamp. This allows data to be extracted from LUSID **as it was** at a point in the past, regardless of any subsequent updates or corrections.

A more concrete example would be how the system will deal with a correction. We can deal with two updates for the same business time (`effectiveAt`) and know that they happened on 2 different `asAt` times. This means we can ask for the state of that entity either before or after the second update/correction.

This enables us to build a system which can always reproduce its state at any point in time. You can ask how the entire system looked `asAt` 5pm yesterday and be guaranteed to get the correct answer. Anything that happened after 5pm would have an `asAt` later than 5pm.