PHP Date Handling: Subtle Pitfalls Subtracting Months

The document explains pitfalls in PHP's Carbon date handling when performing month arithmetic: subMonth() can preserve the day component and cause unexpected month-end overflow (e.g., 2022-12-31 -> subMonth() -> 2022-12-01). It shows that applying startOfMonth() first or using subMonthNoOverflow() yields the intended previous-month results and recommends those approaches to avoid incorrect date calculations.