US Equities Market Holidays

How to use it

Rows are effective-dated. Answer point-in-time questions with the row in force on the as-of date, never the latest row. SecId and ASID are both durable AlgoSeek security keys but different values (the ASID lookup links them); tickers are reused across companies, so resolve a ticker to a key with a trade date.

Typical use

Point-in-time security identity, corporate-action adjustment, and universe construction for US equities.

Limitations

Vendor-curated reference data: rows can be restated when AlgoSeek learns of a late or corrected event, so land each delivery as a snapshot rather than overwriting history. Meaning: a TradeDate in holidays.csv is a weekday full-closure date; the sample contains weekdays only (Mon-Fri) and uses observed dates (e.g. 20051226 when Christmas fell on a Sunday, no 20000101 when New Year's Day fell on a Saturday), so weekends are NOT listed and consumers must combine the list with a weekend rule. Sample includes ad hoc closures as well as scheduled holidays (20010911-20010914 September 11 closure, 20040611 and 20070102 national days of mourning), so the list is the set of actual closures, not just statutory holidays. Early closes (earlycloses.csv, guide Tables 2 and 4): columns TradeDate (string yyyymmdd), MarketOpen (string HH:MM), MarketClose (string HH:MM); guide sample dates 20181224, 20190703, 20191129, 20191224, 20201127, 20201224, 20211126, 20221125, 20230703, 20231124, each 09:30-13:00. A date in earlycloses.csv is a trading day with a shortened session; it should not be in holidays.csv. Use cases per guide: avoid alerting on missing data on holidays, avoid alerting on a shortened feed on scheduled early-close days, and detect unscheduled historical feed cut-offs by comparing against early closes.

Coverage

Holidays and early closes from 1998 through the end of the year following the current year (forward-looking). Applies to US equity and equity options markets. The guide points to the NYSE hours and calendars page for further reference.

Usage constraints

• Licensed vendor data: never export raw rows to a tenant-local destination or include them verbatim in a public artifact; serve only through entitlement-checked platform reads.
• Do not treat the vendor's `Ticker` as a stable identity across time; join on an AlgoSeek security key (SecId or ASID, which are distinct) or the platform symbol mapping.

Known issues (6)

• Primary key is inferred; AlgoSeek's guide does not name one.
• Update cadence and publication latency are not stated in the guide; confirm with AlgoSeek (or GET /v1/meta/datasets/{id}/status).
• Documentation discrepancyPage description says the dataset covers 'full market holidays and early market closes'; the published sample (eq_market_holidays.csv, header TradeDate) contains only the holiday dates. Early closes are a separate file, earlycloses.csv, with columns TradeDate, MarketOpen, MarketClose (guide Table 4); that file is not in the catalog sample.
• Documentation discrepancyThe guide matches the public files named in the task: holidays.csv has the single header TradeDate and earlycloses.csv has TradeDate, MarketOpen, MarketClose; the guide's Table 2 early-close sample is garbled in text extraction but shows 09:30 / 13:00 for every row.
• Documentation discrepancyGuide cover is version 1.1 (Aug 2026) while the guide describes data 'through the end of the year following the current year'; the 100-row sample ends 20080704 (sample is truncated, not a coverage statement).
• Documentation discrepancyGuide gives no Missing column and no refresh cadence for the files.