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Add ?as_of=DATE to any macro series query. The API returns observations using only data published on or before that date.

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Why this exists

Economic data gets revised. The BEA published Q3 2023 GDP on October 26, 2023 as $22,491.567B. Over the next two years, that same quarter was revised four more times, landing at $22,840.989B. If you run a backtest using today’s values, your model had access to information that didn’t exist at the time. The as_of parameter prevents that.

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FRED’s approach vs. ours

FRED’s vintage API (ALFRED) exposes the same data, but requires you to think in terms of realtime_start, realtime_end, and output_type: 
# ALFRED — 8 parameters, 3 date concepts
curl "https://api.stlouisfed.org/fred/series/observations\
?series_id=GDPC1\
&api_key=YOUR_KEY\
&file_type=json\
&realtime_start=2023-10-26\
&realtime_end=2023-10-26\
&observation_start=2020-01-01\
&observation_end=2023-12-31\
&output_type=2"
Vintl wraps the same concept into one parameter: 
curl -H "X-API-Key: $VINTL_API_KEY" \
  "https://api.vintl.io/v1/series/GDPC1/observations?as_of=2023-10-26"
Response
{
  "object": "observation_series",
  "request_id": "req_...",
  "status": "ok",
  "series": { "id": "GDPC1", "title": "Real Gross Domestic Product", "frequency": "Q" },
  "as_of": "2023-10-26",
  "results": [
    { "date": "2023-07-01T00:00:00Z", "value": "22491.567", "as_of_date": "2023-10-26T00:00:00Z" },
    { "date": "2023-04-01T00:00:00Z", "value": "22225.35", "as_of_date": "2023-09-28T00:00:00Z" },
    { "date": "2023-01-01T00:00:00Z", "value": "22112.329", "as_of_date": "2023-09-28T00:00:00Z" }
  ],
  "results_count": 3,
  "has_more": true
}
The value "22491.567" is the advance estimate — the number BEA published on October 26, 2023.

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How as_of resolves

When you pass ?as_of=2023-10-26, the API finds the most recent vintage of each observation published on or before that date. For Q3 2023 GDP (date: 2023-07-01): the advance estimate was published on 2023-10-26, so you get "22491.567". For Q2 2023 GDP (date: 2023-04-01): the latest revision before October 26 was published on 2023-09-28, so you get "22225.35". Without as_of, the API returns the latest revised value for each observation.

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Viewing the full revision trail

Use the revisions endpoint to see how a specific data point changed over time: 
curl -H "X-API-Key: $VINTL_API_KEY" \
  "https://api.vintl.io/v1/series/GDPC1/revisions?date=2023-07-01"
PublishedValueWhat changed
2023-10-2622,491.567Advance estimate
2023-11-2922,506.365Second estimate (+$14.8B)
2023-12-2122,490.692Third estimate (-$15.7B)
2024-09-2622,780.933Annual revision (+$290.2B)
2025-09-2522,840.989Annual revision (+$60.1B)
See Understanding data revisions for more on why these happen and which series are affected.

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Common use cases

Backtesting — Run your strategy against data-as-known. Query each decision date with ?as_of= set to that date. Your PnL reflects decisions you could actually have made. Regulatory models — Basel and Solvency II models require data-as-known, not data-as-revised. The as_of parameter gives you an auditable trail of what inputs the model used. Research replication — Academic papers reference data available at publication time. Point-in-time queries let you reconstruct the exact dataset the authors worked with. Agent grounding — When an LLM reasons about “what was the economy doing in October 2023?”, it needs October 2023’s data, not today’s revision. Feed as_of responses as function calling output.
Last modified on March 29, 2026