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Applies to:
  • Plan -
  • Deployment -

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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.

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Resolution steps

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If you need to preserve the original timezone offset:

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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. 
{
  "startTime": "2026-07-03T08:30:00+01:00",
  "startTimeOffset": "+01:00"
}

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Otherwise, if you want to prevent UTC conversion entirely:

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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. 
{
  "startTime": "2026-07-03T08:30:00 +01:00"
}

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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.