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

# Timestamps converted to UTC in traces

export const plans_0 = "Any"

export const deployments_0 = "Any"

export const data_plane_version_0 = undefined

export const use_case_0 = "Use case - Sending traces with timezone-aware timestamps and seeing them converted to UTC in Braintrust"

<Note>
  **Applies to:**

  * Plan - {plans_0}
  * Deployment - {deployments_0}
  * {data_plane_version_0}
  * {use_case_0}
</Note>

## Summary

**Issue:** Timestamps sent with timezone offsets appear converted to UTC in Braintrust traces — for example, `2026-07-03T08:30:00+01:00` is stored and displayed as `2026-07-03T07:30:00Z`.

**Cause:** Brainstore automatically normalizes any field that parses as `RFC3339` to UTC at index time.

**Resolution:** Store the original UTC offset in a separate metadata field alongside the datetime field.

## Resolution steps

### If you need to preserve the original timezone offset:

#### Step 1: Add a separate field for the offset

Store the offset as a plain string in a companion field. This keeps your datetime field functional for filtering and date operators.

```json theme={"theme":{"light":"github-light","dark":"github-dark-dimmed"}}
{
  "startTime": "2026-07-03T08:30:00+01:00",
  "startTimeOffset": "+01:00"
}
```

### Otherwise, if you want to prevent UTC conversion entirely:

#### Step 1: Store the value as a non-parseable string

Insert a space before the offset to cause the datetime cast to fail. Brainstore will then store the value as a plain string.

```json theme={"theme":{"light":"github-light","dark":"github-dark-dimmed"}}
{
  "startTime": "2026-07-03T08:30:00 +01:00"
}
```

#### Understand the tradeoff

Fields stored as strings are **not** indexed as datetime. This means:

* Date operators are unavailable when querying
* Filtering on this field will be less efficient

This approach is not recommended unless datetime querying is unnecessary for the field.