Unify everything to UTC first, then resample candles to your analysis interval using explicit, documented rules. Align window calculations to close timestamps so rolling metrics compare like with like. When sources disagree on boundaries, choose one canonical anchor and convert the rest deterministically. These small, careful decisions remove phantom jumps and make multi-asset comparisons honest, allowing volatility overlays to reflect behavior rather than calendar confusion or server habits.
Some prints are obviously broken; others are simply rare. Flag impossible wicks by cross-checking adjacent trades or exchange depth, but avoid trimming genuine spikes that communicate crucial risk. Winsorize only with transparent notes, prefer robust statistics, and preserve raw snapshots for audit. By honoring reality while rejecting nonsense, your visual bands teach caution appropriately, rather than comforting with a sanitized past that never truly existed.
Local caches and small databases like SQLite or DuckDB can transform clumsy hourly pulls into instant refreshes. Store precomputed returns and rolling windows alongside raw frames, with versioned schemas for reproducibility. When an upstream outage hits, your charts still load, annotated as stale. Viewers appreciate continuity, while you enjoy breathing room to investigate. Good caches are less about saving bandwidth and more about protecting attention and trust.
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