---
title: gauge_zero_time() | Tiger Data Docs
description: Calculate the time when the gauge value is predicted to have been zero
---

Early access [1.6.0](https://github.com/timescale/timescaledb-toolkit/releases/tag/1.6.0)

Calculate the time when the gauge value is modeled to have been zero. This is the x-intercept of the linear fit between gauge value and time.

## Samples

Estimate the time when the gauge started

```
SELECT
    id,
    bucket,
    gauge_zero_time(summary)
FROM (
    SELECT
        id,
        time_bucket('15 min'::interval, ts) AS bucket,
        gauge_agg(ts, val) AS summary
    FROM foo
    GROUP BY id, time_bucket('15 min'::interval, ts)
) t
```

## Arguments

The syntax is:

```
gauge_zero_time(
    summary GaugeSummary
) RETURNS TIMESTAMPTZ
```

| Name      | Type           | Default | Required | Description                                                                                                             |
| --------- | -------------- | ------- | -------- | ----------------------------------------------------------------------------------------------------------------------- |
| `summary` | `GaugeSummary` | -       | ✔        | A gauge aggregate created using [`gauge_agg`](/docs/reference/toolkit/counters-and-gauges/gauge_agg/gauge_agg/index.md) |

## Returns

| Column            | Type        | Description                                                  |
| ----------------- | ----------- | ------------------------------------------------------------ |
| gauge\_zero\_time | TIMESTAMPTZ | The time when the gauge value is predicted to have been zero |