> ## Documentation Index
> Fetch the complete documentation index at: https://vaquill.ai/docs/llms.txt
> Use this file to discover all available pages before exploring further.
# Point-in-time law
> Retrieve US statutes, regulations and agency guidance as they read on a past date, with provenance saying whether the text is a published edition, a reconstruction, or unavailable
Ask what a provision said on a date, not just what it says now.
```bash theme={"theme":"github-dark"}
curl "https://api.vaquill.ai/api/v1/us/statutes/section/USC_T29_C8_S207/body?asOf=2019-06-01" \
-H "Authorization: Bearer vq_key_..."
```
`asOf=YYYY-MM-DD` on `GET /us/statutes/section/{actId}/body` returns the section's text as it stood
on that date. It costs the same 6 credits as an ordinary body fetch.
This matters when the question is dated: what an employer's obligation was on the day of the
conduct, which version of a rule a contract signed in 2019 incorporated, what a regulation required
before an amendment. Answering it from today's text is how a confidently wrong answer gets built.
## Every answer says where it came from
The response carries an `asOf` block. **Read `source` before you use the text**, because the same
parameter is answered by two different mechanisms and one of them is an estimate.
| `source` | What you are holding | Charged |
| --------------- | ------------------------------------------------------------------------------------------------- | ---------------- |
| `live` | We captured no change after your date, so today's text is what stood then, as far as we ever saw. | Yes |
| `reconstructed` | Rebuilt from the before-side of the first change we captured after your date. | Yes |
| `unavailable` | We know it changed but cannot rebuild the earlier text. No text is returned. | **No, refunded** |
A fourth outcome is not a `source` value at all: `existed: false` means the earliest thing we ever
captured for this section is its **addition**, and that addition postdates your date, so it
demonstrably did not exist yet. That is an answer, arguably the most valuable one this parameter
gives, so it is charged.
| Field | Meaning |
| --------------- | ------------------------------------------------------------------------------------ |
| `requested` | The date you asked for, echoed back. |
| `source` | `live`, `reconstructed` or `unavailable`. |
| `existed` | False when the section demonstrably did not exist yet on your date. |
| `basisChangeId` | The change event whose before-side supplied this text. Null when `source` is `live`. |
| `observedFrom` | The earliest change we ever captured for this section. |
| `isBounded` | Whether the answer is limited by when capture began. Read this first. |
| `coverage` | The same limit in prose, safe to show a reader verbatim. |
Pass `basisChangeId` to
[`GET /us/statutes/section/{actId}/changes`](/docs/api-guide/concepts/section-intelligence) to see the
event the answer rests on.
**`isBounded: true` means we observed no change affecting that date. That is not the same as
there having been none.**
It is set when your date predates `observedFrom`, or when we captured no change for that section
at all. Change capture began long after the corpus did, and runs per source, so a bounded answer
is our best reconstruction rather than a verified historical text.
Surface it. Rendering a bounded answer as authoritative point-in-time law makes a claim we did
not make.
An `asOf` response never populates `html`, on any corpus. Reconstructed text is plain text, and
synthesising markup the publisher never printed would defeat the point of the endpoint. Use
`text`, or `content` where the corpus supports it.
## Reconstruction versus a published edition
`asOf` resolves two different ways depending on the corpus, and the difference decides how much
weight the answer carries.
For corpora where the publisher issues dated editions, `asOf` resolves to **the edition that
was in force on your date**, served as published. This is the publisher's own artifact, not our
estimate.
Everywhere else, the corpus holds one current text per citation and the earlier one is rebuilt
from observed change history. Accurate to what we captured, bounded by when capture began.
### Corpora that answer from a published edition
| Corpus | How point-in-time works |
| ---------------------- | -------------------------------------------------------------------------------------------------------------------- |
| `CFR_ANNUAL` | 31 GPO annual editions, 1996-2026, all 49 titles. `asOf` resolves to the edition in force. |
| `copyright_compendium` | Three dated releases (2014, 2017, 2021). Resolves to the edition the Copyright Office states applied. |
| `ofac_faq` | 361 prior FAQ versions are **separate citable documents** from OFAC's own archive, served `actStatus: "superseded"`. |
Two behaviours to expect on `CFR_ANNUAL`. **`editionsObserved` is an enumeration, never a range**:
a version observed in 1998, 1999 and 2003 lists exactly those years, and a date in an unobserved
gap returns `asOf.isBounded: false` rather than the nearest year held. **A citation year is the
volume's own `` year, not the folder GPO filed it under**, because GPO reprints unchanged
volumes forward without re-dating them.
### Where history is a separate document rather than a date
Some corpora publish their own prior versions, so you retrieve history by citation instead of by
date. `whd_opinion_letter` keeps withdrawn and superseded letters retrievable under their own
`act_id`, including the 2009 letters WHD re-issued in 2018 under new numbers. A re-issued pair
shares one PDF at the publisher but is two documents with opposite status.
### Where point-in-time is weakest
Corpora whose publisher replaces text in place and issues no superseded editions, such as the CMS
Medicare manuals and the DOL Field Operations Handbook, give us nothing to reconstruct from beyond
our own capture history. Expect `isBounded: true` on dates before capture began.
## Worked example
```bash theme={"theme":"github-dark"}
# What did the FLSA overtime section say before the 2019 salary-threshold rule?
curl "https://api.vaquill.ai/api/v1/us/statutes/section/USC_T29_C8_S207/body?asOf=2019-06-01" \
-H "Authorization: Bearer vq_key_..."
```
```json theme={"theme":"github-dark"}
{
"actId": "USC_T29_C8_S207",
"text": "...",
"asOf": {
"requested": "2019-06-01",
"source": "reconstructed",
"existed": true,
"basisChangeId": 91,
"observedFrom": "2026-08-09T04:10:00Z",
"isBounded": true,
"coverage": "Change capture for this source began 2026-08-09..."
}
}
```
`isBounded: true` here because 2019 predates `observedFrom`. The text is our best reconstruction,
and a product built on it should say so to its reader.
## Choosing the right tool
| Question | Use |
| ---------------------------------------- | ---------------------------------------------------------------------- |
| What did this section say on a date? | `asOf` on `/section/{actId}/body` |
| What changed, and when? | [`/section/{actId}/changes`](/docs/api-guide/concepts/section-intelligence) |
| Give me the whole 2004 CFR as printed | `corpusType=CFR_ANNUAL` |
| Tell me when it changes from now on | [Law change alerts](/docs/api-guide/alerts) |
| Which sections moved since my last sync? | `changedSince` on `/statutes/search` |
`actStatus`, `goodLawStatus`, and whether a section is still operative.
Which corpora hold editions, and how far back each one reaches.