Rolling 90-Day Period: Definition, Calculation, and Business Applications

A rolling 90-day period (or trailing 90 days) is a dynamic time window that advances one day at a time, always covering the most recent 90 calendar days.

Calculation Example

• Today: January 15 → window: October 17 – January 15
• Tomorrow: January 16 → window: October 18 – January 16

Business Uses

• Performance tracking: Revenue, user engagement, churn, conversion rates — smooths daily volatility.
• Compliance: Regulatory limits (e.g., 90-day prescribing windows, rolling averages for emissions).
• Financial: Rolling 90-day cash flow, DSO, inventory turnover.
• Clinical: Medication adherence (PDC), readmission rates.

Advantages Over Fixed Periods

• Always current — no "stale" quarter-end snapshots.
• Reveals trends and inflection points earlier.
• Enables real-time decision-making.

Implemented via SQL window functions, BI tools (Tableau, Power BI), or spreadsheet formulas (OFFSET, INDEX).