SPY (via the ETF and futures) keeps trading after the 4pm close, and big after-hours sessions — mega-cap earnings, a late headline — carve out a range from roughly 4pm to 8pm. Those after-hours highs and lows don't vanish overnight; they become reference levels the next session reacts to.
Why they matter next day
An after-hours extreme is a price the market already found meaningful once — where a move stalled or reversed on the news. Resting orders and memory cluster there, so when the cash session approaches an after-hours high or low, price tends to react. They fill the gap between the prior-day range and the pre-market range as part of the overnight structure.
How to use them
Mark the prior after-hours high and low alongside the prior-day and pre-market levels. Trade them like any session level: a rejection is a fade, a held break is continuation. They're especially relevant after an event-driven after-hours move, when they mark where the news-driven repricing topped and bottomed — the levels the next day's participants are anchored to.
Where SPY reacted to the news at 5pm is a level at 9:30. The after-hours range is overnight structure, not overnight noise.
The caveat
After-hours liquidity is thin, so an after-hours extreme set on tiny volume is a weaker level than one carved on heavy post-earnings trade — weight them by how much really traded there. And a fresh overnight gap can leapfrog them entirely. Used as one layer of the overnight map — confirmed by confluence with other levels — after-hours levels add real structure to the first hour. NoVo folds the relevant session levels into the map so you're not rebuilding them by hand each morning.