---
title: timestampDiff
description: Pipeline expression helper that returns the difference between two timestamps in a chosen unit.
next: /firestore/pipelines/timestamp-extract
previous: /firestore/pipelines/switch-on
---

`timestampDiff()` calculates how much time separates an **end** timestamp from a **start** timestamp, expressed in the unit you choose (`day`, `hour`, `minute`, and so on).

Import from the pipelines entry point:

```js
import { timestampDiff, field } from '@react-native-firebase/firestore/pipelines';
```

# Basic example

```js
import { getFirestore } from '@react-native-firebase/firestore';
import { execute, field, timestampDiff } from '@react-native-firebase/firestore/pipelines';

const db = getFirestore('your-enterprise-database-id');

const snapshot = await execute(
  db
    .pipeline()
    .collection('events')
    .select(
      timestampDiff(field('endTime'), field('startTime'), 'day').as('daysApart'),
      timestampDiff('endTime', 'startTime', 'hour').as('hoursApart'),
    ),
);

snapshot.results.forEach(row => {
  console.log(row.data().daysApart, row.data().hoursApart);
});
```

# Related helpers

| Helper              | Use when                                         |
| ------------------- | ------------------------------------------------ |
| `timestampDiff`     | Measure elapsed time between two timestamps      |
| `timestampAdd`      | Shift a timestamp forward by an amount           |
| `timestampSubtract` | Shift a timestamp backward by an amount          |
| `TimeUnit`          | Type for `'microsecond'` … `'day'` unit literals |

# Upstream reference

See the [firebase-js-sdk `timestampDiff` declaration](https://firebase.google.com/docs/reference/js/firestore_pipelines#timestampdiff) for full overload signatures.