Regulation NMS defines regular trading hours as 9:30 a.m. to 4:00 p.m. Eastern Time, or another time period determined under the referenced rule provision. The definition is regulatory and U.S.-market specific; extended-hours sessions and venue-specific schedules are separate concepts.
ReviewedEvidence1 sourceSectionPhrases & Idioms
Quick answer
For Regulation NMS questions, regular trading hours is a defined U.S. market time window rather than a generic synonym for all hours in which a security can trade.
Key details
Canonical FormRegular Trading Hours
Core MeaningRegulation NMS defines regular trading hours as 9:30 a.m. to 4:00 p.m. Eastern Time, or another time period determined under the referenced rule provision.
Further guidance
History Boundary
The definition is regulatory and U.S.-market specific; extended-hours sessions and venue-specific schedules are separate concepts.
Meaning
For Regulation NMS questions, regular trading hours is a defined U.S. market time window rather than a generic synonym for all hours in which a security can trade.
Usage Boundary
The definition is regulatory and U.S.-market specific; extended-hours sessions and venue-specific schedules are separate concepts.
Sources and evidence
Sources are shown with the role they play in this guide. Historical or style-sensitive claims are kept within the evidence boundary described above.
Alternative Trading System is a current federal securities-regulation defined term. This guide preserves the rule-specific definition and boundaries instead of replacing it with informal market shorthand.
Under current U.S. Regulation NMS, an “automated trading center” is a trading center with systems, procedures, and rules capable of displaying automated quotations, identifying non-automated quotations as manual, and applying reasonable standards for changes between automated and manual status. This is a condensed rule-scoped explanation of 17 CFR § 242.600; the full definition contains multiple operational conditions and should be consulted for compliance work.
A defined Regulation NMS facility operated by or for an exchange or national securities association that executes orders or presents them to members for execution. This page is limited to the Regulation NMS definition; other regulatory or operational uses of “trading facility” may be broader.
Regulation NMS defines trading center broadly to include specified exchanges, association facilities, alternative trading systems, market makers, and other broker-dealers that execute orders internally as principal or crossing agent. This page uses the U.S. Regulation NMS definition; ordinary-language uses of trading center can be broader and should not be substituted for the regulatory term.
Trading Rotation is a current federal securities-regulation defined term. This guide preserves the rule-specific definition and boundaries instead of replacing it with informal market shorthand.
Actionable Indication of Interest is a current federal securities-regulation defined term. This guide preserves the rule-specific definition and boundaries instead of replacing it with informal market shorthand.
Administrative Data is a current Regulation NMS defined term for specified administrative, control, and technical messages in the market-data plan framework.
Affiliate of a Subscriber is a current Regulation ATS defined term. This guide preserves the rule-specific meaning and boundary instead of replacing it with informal market shorthand.
