Timeframe aliasing: when the chart's rhythm shapes the pattern

[Shadow Trader]

On a five-minute chart, bars start at :00, :05, :10. A strategy keyed to those bars sees signals only at those moments. Shift the start by one minute, using a chart with bars at :01, :06, :11, and the signals change.

That's aliasing. The pattern depends on the sampling grid. A "breakout of the previous bar's high" differs when the bar boundaries move, since the highs and lows are measured over different windows.

The consequence is that results from a strategy can depend heavily on arbitrary choices, like when the chart's bars begin. Test it by running the same logic with the grid offset by one, two, three minutes. A robust strategy gives similar results. A fragile one swings.

In real markets, other participants also use time grids. Many orders and algorithms trigger at the open of five-minute, fifteen-minute, and hourly bars, so the standard grid has real activity concentrated at specific moments. That's why reactions at exactly :00 or :30 are common.

The aligned grid might be a feature, not just an artifact.

Does the strategy survive a one or two minute shift in the bar grid, or does it fall apart?