## TL;DR

Negative (pre-1970) timestamps are not supported: the backend parses the timestamp field as an unsigned 64-bit integer, so a negative value 500s, and Dust's team decided not to add support.

## Steps

1. Negative (pre-1970) timestamps are not supported: the backend parses the timestamp field as an unsigned 64-bit integer, so a negative value 500s, and Dust's team decided not to add support. The unit is milliseconds, not seconds as old docs stated. Workaround from the thread: don't rely on the timestamp field, put human-readable dates at the top of the document text (e.g. `$createdAt: 1966-08-20`), which retrieval does match, and for hard date filters use document labels/tags with the in-conversation tag-filtering feature instead.

## When to use

You are seeing this: Using the Dust upsert-document API (POST /api/v1/w/{wId}/spaces/{spaceId}/data_sources/{dsId}/documents/{documentId}), passing a negative Unix timestamp for document dates before 1970 (e.g. -106245523000 for August 1966) blew up with a 500. Use this skill when you run into "Dust upsert document API returns 500 on negative (pre-1970) timestamps".

## When not to use

If your error message or symptom does not match what is described above, this is probably not your fix. Search for your exact error text instead of forcing this one to fit.

## Versions

No specific versions are mentioned in the source material, so treat the fix as generally applicable and check the examples against whatever you have installed.

## Why this happens

The original report does not dig into a root cause. It documents the symptom and the fix that resolved it.