Date worksheets look trivial until weekends, leap days, and inclusive end dates disagree with a spreadsheet. The calculators document their counting rules so project and HR planning stays reproducible.

Days-between returns the difference according to the page’s inclusive/exclusive convention. Always match that convention to your contract language before you rely on the number.

Working-day tools remove weekends and optional holidays. Age tools decompose the span into years, months, and days from a birth date. Use the date calculator when you need “N days from today” rather than a difference.