US Stock & Options Market Data Reference

How do AM and PM settlement differ for SPX and SPXW options?

Standard SPX monthly options are AM-settled using opening prices; SPXW options are PM-settled using closing prices. AM/PM settlement describes how the settlement value is calculated, while exercise style describes when the holder may exercise. Settlement depends on the contract series, not simply on whether the underlying is an index.

When interpreting historical options records, identify the contract root, expiration and rules in force for that period. Contractual expiration, last trading time and settlement calculation are separate concepts. A present-day specification alone may not describe an older series, and absence of an expiration-day trade is not, by itself, proof of AM settlement.

HistoricalData.net options CSV files record the archive's settlement classification in settlement_time; a blank means unknown. HistoricalData.net's daily time-to-expiry convention for calculating options IV and Greeks is a modelling convention, not an exact intraday trading clock.

Contract reference: Cboe SPX/SPXW specifications.

Are US index options always European-style?

US index options can use American-style or European-style exercise. OEX and XEO both reference the S&P 100, but OEX allows American-style exercise and XEO uses European-style exercise. The underlying's asset class alone does not determine the appropriate pricing model.

An option's exercise style and settlement convention must be read separately. European-style exercise does not imply PM settlement, and an AM settlement label does not establish exercise style. HistoricalData.net options CSV files record these properties in style and settlement_time.

Contract references: Cboe OEX and Cboe XEO.

When did standard US monthly options expirations move from Saturday to Friday?

The Options Clearing Corporation (OCC) changed the standard expiration convention for applicable US options expiring on or after 1 February 2015 from the Saturday after the third Friday to the third Friday. Exchange holidays and designated grandfathered expirations have exceptions; the rule does not apply uniformly to every options product.

Historical options analysis should preserve the contractual expiration date in the source record and resolve last trading time and settlement from the relevant series and calendar. Earlier standard monthlies commonly carry Saturday dates. An older contract need not have last traded on Friday, and a post-transition Saturday date is not automatically an error.

Historical rule and exceptions: OCC By-Laws, Article I: Expiration Date. HistoricalData.net's pricing treatment is documented under Options time to expiry.

What time does the US options market close?

US options regular sessions commonly end at 16:00 or 16:15 US Eastern time (ET), depending on the product; selected products also have extended sessions. ET follows EST or EDT as applicable. Expiration-day and holiday schedules can differ from ordinary trading days, so no single close applies to every option series and date.

A US options session from 09:30 to 16:00 ET lasts 390 minutes; 09:30 to 16:15 ET lasts 405 minutes. A 09:30–13:00 ET early session lasts 210 minutes, but that is not a universal half-day schedule. Measure options trading activity and quote age against a calendar for the relevant product and historical date.

An options trade timestamp after 16:00 ET does not by itself establish a late report. The session, timestamp definition and trade condition must also be checked. Historical session rules can change over time.

Schedule reference: Cboe options hours and holidays; consult the relevant product specification for expiration-day hours.

When does HistoricalData.net multi-leg volume coverage begin?

HistoricalData.net options multileg_volume coverage begins on 4 November 2019, when the source records begin carrying the required detailed trade conditions. Earlier values are blank and mean unknown, not zero multi-leg activity. The date is a source-coverage boundary, not the introduction date of multi-leg trading or exchange reporting.

An options archive's price-history start date does not establish the start date of every derived field. HistoricalData.net lists each field's availability in the options column definitions. Numeric trade-condition codes must be interpreted using the relevant source's definitions; see HistoricalData.net trade aggregation.

How common is multi-leg activity among traded option contracts?

In six HistoricalData.net source-data samples spanning 4 November 2019 to 25 August 2026, 42%–54% of option contracts with trades had reported multi-leg activity. For 12%–21% of traded contracts, reported multi-leg volume matched or exceeded the day's total volume. Each percentage uses traded option contracts on one sampled day as its denominator, not all listed contracts or total market volume.

Sample dates: 4 November 2019, 15 June 2020, 15 March 2021, 15 December 2021, 15 June 2022 and 25 August 2026. The ranges describe these six sessions, not every day in the archive.

An option contract's reported volume can include activity executed as part of a multi-leg order. Multi-leg activity alone does not demonstrate that an order for that contract alone could have filled at the same price or size. Compare multileg_volume with quotes and trade activity, using the options aggregation conventions.

Do trade-condition volume categories add up to total option volume?

Trade-condition volume categories add up to total option volume only when the categories are mutually exclusive, cover all trades and use the same aggregation rules. A trade can carry several condition codes, so category totals must be checked before treating them as separate parts of a whole.

In HistoricalData.net options files, reported multileg_volume can exceed volume. Subtracting multileg_volume from volume does not reliably establish the number of contracts traded outside multi-leg orders. Check the field's interpretation before using the difference.

How many minutes do traded option contracts actually trade in?

In HistoricalData.net's options source-data measurement on 1 June 2026, the median contract traded in two distinct one-minute intervals among 392,561 contracts with observed trades in the source minute aggregates. The result describes traded contracts in one session, not the typical behaviour of every listed option.

HistoricalData.net options active_minutes counts one-minute intervals containing trades. The field describes how dispersed recorded trading activity was; it does not measure quote depth, the ability to fill an order, or activity in minutes without trades.

Do stock and options minute-bar volumes sum to daily volume?

Options source comparison

In HistoricalData.net's options source comparison on 1 June 2026, summed minute volume matched daily volume for 392,180 of the 392,545 contracts present in both aggregates: 99.91%. Another 16 contracts appeared only in the minute aggregates and are excluded from that denominator.

HistoricalData.net delivers end-of-day options chains; the options minute aggregates in this comparison are source data used for validation. The observed mismatch rate is not a tolerance for other dates. Differences in coverage, session boundaries, corrections and aggregation rules need to be checked when investigating a discrepancy.

Stock source comparison

Summing stock minute-bar volume does not necessarily reproduce stock daily volume. HistoricalData.net's 2026 stock source comparison through 24 August 2026 measured volume ratios only for symbol-days with both daily and minute aggregates; days without minute records were counted separately.

The 2026 stock comparison spans many sessions and has a different population from the options comparison on 1 June 2026. A symbol-day means one stock symbol on one trading date. See stock data limits for the coverage implications.

Why does a current US ticker list omit delisted stocks?

A current US stock ticker list omits securities that previously traded and then delisted. Delistings include acquisitions and other listing changes as well as business failures; delisted does not mean worthless. Using only today's listings to select a historical backtest universe can introduce survivorship bias.

HistoricalData.net stock archive counts describe the securities covered under the archive's classification rules. The counts do not measure the share of US market value that disappeared or the return bias in a particular strategy. Historical universe construction requires eligibility for each date and separate listing lifetimes for reused symbols where the records support them.

HistoricalData.net's survivorship guide covers universe construction, symbol reuse and terminal portfolio values. Current archive coverage is listed on the stock data page.

How should HistoricalData.net market-data measurements be cited?

A citation of HistoricalData.net's market-data measurements should retain the instrument type, sample dates, measured population, denominator and exclusions. The measurements in this reference are fixed source-sample observations, not daily coverage counters or guarantees for unmeasured dates.

To report a discrepancy in this market data reference, send the section link, date, symbol or contract, and a reproducible example to info@historicaldata.net.