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How can changed period boundaries make a growth comparison misleading?
Inspect the length and dates of both reporting periods before interpreting a change in totals.
Two year labels can hide different intervals
A year-on-year comparison needs the actual start and end dates of both periods. A changed year end or a weekday-based reporting calendar can change the interval length. A larger total over a longer interval should not automatically be described as the same-duration growth rate.
Do not erase the date distinction by grouping solely on the end year. Keep the reported values and boundaries available before choosing an analytical adjustment. This reference does not normalize periods to a standard day count.
Use a bounded comparison
For the two Apple revenue rows below, the intervals are 1 October 2023–28 September 2024 and 29 September 2024–27 September 2025. They remain the dates actually reported rather than two invented January–December periods.
If a difference in length matters to the question, describe it explicitly and use a separately justified method. Do not silently annualize a total or infer missing quarterly values from the selected annual rows.
Reported source example
Apple Inc. · CIK 320193 · Revenue
| Reported value | Unit | Period type | Start | End | Concept | Filed | Filing FY / FP | Frame | Source filing |
|---|---|---|---|---|---|---|---|---|---|
| 391035000000 | USD | duration | 2023-10-01 | 2024-09-28 | us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax | 2025-10-31 | 2025 / FY | CY2024 | 10-K · 0000320193-25-000079 |
Reported source example
Apple Inc. · CIK 320193 · Revenue
| Reported value | Unit | Period type | Start | End | Concept | Filed | Filing FY / FP | Frame | Source filing |
|---|---|---|---|---|---|---|---|---|---|
| 416161000000 | USD | duration | 2024-09-29 | 2025-09-27 | us-gaap:RevenueFromContractWithCustomerExcludingAssessedTax | 2025-10-31 | 2025 / FY | CY2025 | 10-K · 0000320193-25-000079 |