---
title: "US recession dates (NBER Business Cycle Dating Committee)"
method: GET
path: "/api/v1/research/nber/recession-dates"
tags: ["Research"]
---

# US recession dates (NBER Business Cycle Dating Committee)

`GET /api/v1/research/nber/recession-dates`

Canonical US business cycle peaks and troughs as dated by the National Bureau of Economic Research (NBER) Business Cycle Dating Committee. Returns 35 cycles spanning December 1854 through the April 2020 trough. Each record includes the peak and trough months (YYYY-MM), the same dates as full ISO 8601 UTC timestamps (day 1 of the month), and the recession duration in months. Sourced from the static JSON file at `data.nber.org/data/cycles/business_cycle_dates.json`. No new recession has been declared by the BCDC since the April 2020 trough, so this dataset changes only when the committee announces a new peak or trough. `limit` returns only the N most recent cycles; without it all 35 are returned, oldest first.

## Query parameters

- `limit` integer, nullable — Return only the N most recent business cycles. The full dataset holds 35 cycles; omitting the parameter returns all of them. Order stays oldest-first either way.

## Response `200`

List of NBER-dated US business cycles, oldest first, with peak, trough, and duration in months. With `limit`, the N most recent cycles in the same oldest-first order.

- EnvelopeNberRecessionDatesPayload
  - `data` NberRecessionDatesPayload, required — Canonical US business cycle peaks and troughs from the NBER Business Cycle Dating Committee.
    - `source_url` string, required — Upstream NBER URL used to produce this response.
    - `count` integer, required — Number of business cycles returned in this response. 35 without `limit`; equal to `limit` when the parameter narrows the list.
    - `recessions` NberRecession[], required — Ordered list of US business cycles (oldest first) as dated by the NBER Business Cycle Dating Committee. The full dataset is 35 cycles from December 1854 through the April 2020 trough; with `limit` only the N most recent are returned, same order.
      - `peak` string, nullable — Calendar month of the business cycle peak (YYYY-MM). Null for the first entry, which records only the December 1854 trough without a corresponding peak.
      - `trough` string, nullable — Calendar month of the business cycle trough (YYYY-MM).
      - `peak_date` string, nullable — First day of the peak month as a full ISO 8601 UTC timestamp. Null when `peak` is null.
      - `trough_date` string, nullable — First day of the trough month as a full ISO 8601 UTC timestamp.
      - `duration_months` integer, nullable — Number of months from peak to trough (recession length). Null when `peak` is null or the cycle is open.
  - `meta` SugraMeta, required — Metadata on a /api/v1/* response envelope built through `helpers.response.sugra_response`, which is how routes are expected to answer. A route that assembles its own `meta` dict carries only the keys it writes itself, so an optional field below can be absent because this response has nothing to report OR because that route does not build its envelope here - the two are not distinguishable from the outside (API-43).
    - `endpoint` string, required — Requested endpoint path.
    - `data_time` string, required — ISO 8601 timestamp the data on this response is stamped with. It is the source's own timestamp whenever the source supplied one this API could read; when it did not, this field falls back to the value of `response_time` and `data_age_days` is omitted, so the PRESENCE of that field is the signal to read - with the one exception named in its own description, a route that substitutes its own current time for a source timestamp it never received. Usually UTC (`Z`), but a source stating its own numeric offset keeps it (2026-04-16T14:30:00+09:00) rather than being converted a second time. For a source that publishes by period this is the period's START (see `period`) and for one that publishes by calendar day it is that day's midnight - in neither case a moment at which anything was observed or released.
    - `response_time` string, required — ISO 8601 UTC timestamp when this response was produced.
    - `provider` string, required — API name and version.
    - `data_age_days` number, nullable — Age of the data in days at the moment this response was produced, i.e. `response_time` minus `data_time`. Present ONLY when the timestamp this response is stamped with is a clock time that could be read as a real instant. It is ABSENT - never 0 - in every other case. Absent when no readable source timestamp was supplied, because `data_time` then repeats `response_time` and a zero age would assert that the data is current precisely where its true age is unknown. Absent when the source names a calendar day, a month, a quarter or a year (see `period`): the instant is then a boundary this API anchored at midnight, and time since a day or a quarter BEGAN is a different quantity from the age of the data - a daily series is out by up to a day, a quarterly one by up to a quarter. A midnight counts as such a boundary whichever zone it is stated in, and whether the source stated it or this API anchored it. The one case this field cannot see is a route that substitutes its own current time for a source timestamp it never received: the substituted value is a real, readable instant and is indistinguishable from one the source stated, so the age reads as roughly 0. The shared cache-and-fetch helper behind most routes stopped doing that (API-43), but the presence of this field is a statement about the timestamp the response carries, not a guarantee about the route that supplied it. Rounded to 0.001 day (86.4 seconds), so 0.0 is a real measured age anywhere within roughly +/-43 seconds and not a stand-in for unknown; a source stamping an instant in the future reports a negative value (-0.001 or less) rather than being clamped. Sources publish on very different cadences, so a non-zero age is normal, not an error. Preserve absence in client code: a generated client that materialises a missing optional number as its numeric default turns 'age unknown' back into 'age zero', which is the exact confusion this field exists to remove.
    - `source` string, nullable — Identifier of the primary upstream source used for this response.
    - `attribution` string, nullable — Human-readable attribution mandated by an upstream source (e.g. a securities regulator or self-regulatory organization). Present only on responses whose source requires the owner and source to be clearly identified. Do not remove or alter it when using the response.
    - `fallback_used` boolean, nullable — True when the primary source failed and a fallback produced the data.
    - `fallback_chain` string[], nullable — Ordered list of sources attempted, in the order they were tried.
    - `cached` boolean, nullable — True when this response was served from the internal cache.
    - `stale` boolean, nullable — True when the cached response was returned after the upstream rate-limited or errored. Clients can use this to detect degraded data.
    - `period` string, nullable — Unit of observation, when the source publishes by period rather than by instant. `data_time` carries the period's START instant so it stays machine-readable; this field preserves what that instant used to mean, which the conversion would otherwise erase. Present only for such sources, and only when the source hands the API the label itself - a client that converts the period to its start instant before building the envelope loses the label, though not the age exclusion, which is decided by the instant. Note that `data_age_days` is omitted whenever this is present, because an age measured from a period start is not a freshness figure.
    - `notes` string, nullable — Data-quality caveat about THIS response - how old the underlying report is, a chokepoint AIS lower-bound, or that a source-reported `data_time` could not be read and the response time is shown instead. Distinct from `attribution`, which is a licensing obligation. Multiple caveats are joined with ' | '. Present only when there is one.

## Other responses

- `401` — Missing or invalid `x-api-key` header. JSON body with a stable `code` distinguishing `missing_api_key` (no header sent) from `invalid_api_key` (header sent, key not accepted); any other 401 source carries the generic `unauthorized` with its detail as `reason`. Plus `hint`. `plan` is always null on 401 - an unauthenticated request has no plan; quota exhaustion is 429, not 401.
- `422` — Validation Error
- `429` — Daily rate limit exceeded. Check `X-RateLimit-Reset` for the next window.
- `503` — Upstream source is temporarily unavailable. Retry after a short delay.

## Changes

- **2026-09-01** `328d061c12ca` — 3 info
  - added the optional property `meta/data_age_days` to the response with the `200` status
  - added the optional property `meta/notes` to the response with the `200` status
  - added the optional property `meta/period` to the response with the `200` status
- **2026-08-08** `4c4530760ba1` — 12 info
  - added the optional property `code` to the response with the `401` status
  - added the optional property `code` to the response with the `429` status
  - added the optional property `code` to the response with the `503` status
  - added the optional property `hint` to the response with the `401` status
  - …8 more
- **2026-08-08** `4e2740743eb4` — 2 info
  - added the new optional `query` request parameter `limit`
  - added the non-success response with the status `422`

[Change history](https://skmtc.dev/sugra/apis/sugra-api/changes/api/v1/research/nber/recession-dates/get.md)

---

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