Days Between Dates Calculator

This tool computes the number of days between two dates for planning, scheduling, and deadline estimation. It supports two modes: calendar days by default and business days when weekends and optional holidays are excluded. It accepts dates in YYYY-MM-DD format and returns clear day counts for downstream planning.
Conceptually, dates are normalized to internal date objects, differences are calculated in whole days, and rules for inclusivity are applied. In business-days mode, the calculator iterates the date range, counting weekdays (Mon–Fri) and skipping any holidays supplied by the user.
Who benefits: project managers, schedulers, educators, and analysts who need duration estimates to align teams and milestones. Unique value: explicit control over inclusive endpoints and a straightforward, export-ready day count without scheduling complexity.
Core features include two-input date range, mode selection, optional inclusive flag, optional holidays, and output of calendar_days and business_days. Typical use cases: task duration, travel planning, SLA windows, and deadline confirmation.