At a glance
The short version
The New York open produces more of the day's range than any other hour on the US indices, and it is the window where a hesitant entry costs the most. It is also the one session where the difference between the cash open and the futures session quietly ruins backtests — because a range built off overnight price is not the range anyone is trading.
The RTH problem, and how this fixes it
Index futures trade nearly around the clock. So "today's high", "the opening range" and "the previous day's low" all have two answers: one from the full futures session and one from the 09:30–16:00 cash session that equity traders actually watch. Backtest the wrong one and every level you mark is a few points away from the level other people are reacting to.
CRTLAB carries regular-trading-hours variants of all three US indices alongside the full-session ones. This page opens the RTH Nasdaq specifically, so the opening range is built from the cash open and nothing else. That single choice changes an opening-range backtest more than most parameter tuning does.
What to measure in the New York window
The killzone CRTLAB shades runs 07:00–10:00 New York time for the AM session, and 13:30–16:00 for the PM. Those bounds matter for the test: a strategy that works from 09:30 to 10:00 and loses from 10:00 to 11:00 shows up as mediocre unless you split it.
The three things worth logging separately are the opening range break, the sweep of the prior day's high or low in the first hour, and the reaction at the daily open. Most "New York strategies" are one of those three with different vocabulary.
Which instrument
NAS100 is the fastest and the most punishing; SP500 is the smoothest; US30 sits between them and is more sensitive to single large-cap moves. Same open, three different personalities — and running one rule set across all three in an afternoon is how you find out which one your temperament actually suits.
Frequently asked questions
What time is the New York killzone?
CRTLAB shades New York AM from 07:00 to 10:00 New York time and New York PM from 13:30 to 16:00. Shading paints at 5 minutes and below.
Can I backtest only the cash session?
Yes — CRTLAB carries regular-trading-hours variants of NAS100, SP500 and US30 alongside the full futures sessions, so an opening range can be built from the 09:30 cash open rather than from overnight price.
Is the New York session backtester free?
CRTLAB is free to try. You get the New York killzone on every market, with every tool the product has, for your first 10,000 candles of replay — roughly two hours of stepping through a chart, no card needed. After the sample, unlimited replay is $14.99 a month, cancel any time. Session shading only paints at five minutes and below — that is by design, not a gate.
Should I test the AM and PM sessions together?
No. They are different markets with different participants — the AM carries the day's expansion, the PM often carries the reversal. Averaging them is how a good AM strategy and a bad PM one become one mediocre number.