Previous Day High (PDH)

The previous day high is the high of the prior regular session, unless your feed defines the day differently. Intraday traders use it as a breakout level and as a sentiment line. Trade above it means today has gone beyond yesterday's extreme. It is a fact, not an indicator.

Mark yesterday's high before the open. Do not update it with overnight trades unless your strategy uses the full electronic session and you said so. Cash-session high and futures-session high are different numbers.

A hold above PDH, after a break and a retest, is a common intraday long. Risk goes back below PDH or below the opening range. It is bullish only relative to yesterday, not a view on the monthly trend.

A failure at PDH, especially after a sweep above it that returns inside yesterday's range, is a short location for intraday mean-reversion. The high of the sweep is the stop.

Using a daily candle that includes a different session than the one you trade, so your PDH is a price your market did not treat as the high.

PDH matters most on the day after. A week later it is just an old high, unless it lines up with a larger level.