ETH

What it is

ETH stands for Extended Trading Hours — the after-hours and overnight session for an instrument, running outside the RTH (Regular Trading Hours) cash window. For US equity index futures (ES, NQ, YM, RTY), ETH covers everything outside the 9:30am–4:00pm Eastern cash session: the post-close period, the overnight hours, and the pre-open period leading into the next day's RTH open.

Most major futures contracts now trade close to 24 hours a day on CME Globex, with only short maintenance breaks (typically a one-hour daily break around 5:00pm Eastern for equity index products). All trading inside the Globex window but outside the RTH window is ETH. Across asset classes the ETH definition varies — energy, metals, and FX futures each have their own RTH/ETH split.

ETH is not "low-activity time" by default. The Asian session opens during US ETH, European traders take positions during the latter half of US ETH, and the period leading into RTH often sees significant pre-cash positioning. But the participation profile is different from RTH: less institutional cash-equity flow, more thin pockets, more potential for outsized moves on relatively small order flow.

Why it matters

The split between RTH and ETH matters because the two regimes behave differently. Spreads are wider in ETH, single orders move price further, volume is concentrated at session opens (Asia, Europe), and many institutional execution algos are dialed back or off.

Key consequences for analysis:

• Overnight gaps — the price level at RTH close vs the price level at next-day RTH open often differs significantly. Whether or not the gap "fills" during the new RTH session is a standard reference question.
• Volume profile sensitivity — including ETH in a profile shifts the POC and VAH/VAL, sometimes materially, because ETH adds volume at prices RTH didn't trade.
• Risk management — overnight positions are exposed to ETH liquidity, which means stop slippage risk is non-trivial in fast moves.
• News-driven moves — many macro releases happen outside RTH (Asian central banks, European data). ETH-aware traders track these explicitly.

How it appears on Sierra Chart

Sierra Chart's session model treats ETH as a configurable window per instrument, separate from but adjacent to RTH. Charts can be configured to display only RTH bars, only ETH bars, or both — typically with ETH bars shaded differently or separated by visual session breaks. The platform's session-aware studies (volume profile, ATR, daily statistics) all support RTH-only, ETH-only, or full-session computation modes.

For ACSIL developers, three helpers expose session membership: IsDateTimeInDaySession (RTH only), IsDateTimeInEveningSession (ETH only), and IsDateTimeInSession (any defined session). A study that needs to behave differently inside ETH can branch on these helpers.

Common patterns / pitfalls

• Don't assume "session" means RTH — many built-in study defaults use the full Globex session. Check the session toggle on every study.
• Range bar charts and ETH — Range bars built on ETH-inclusive data can span the RTH→ETH gap. The Open of the next-day RTH bar can equal the prior settle (continuation price) rather than the actual cash open, producing misleading values in studies that read sc.Open. Enabling the ETH session explicitly in the chart's session settings fixes this.
• Sunday open — the Sunday-evening ETH open is often abrupt and thinly traded. Studies that compute "session change" need to handle this edge correctly.
• Maintenance breaks — the short daily break around 5:00pm Eastern is technically inside ETH but trades zero volume. Bars that span the break are not abnormal.
• DST changeover — like RTH, ETH boundaries shift in wall-clock terms during DST changes; Sierra Chart handles this if the chart timezone is correct.

Related SCS studies

Session ATR Percent and the various profile-aware SCS overlays expose session-time inputs so traders can frame their analysis around RTH, ETH, or both. The Trading Journal records every fill with its exchange timestamp, allowing post-hoc analysis of RTH vs ETH performance.