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Date calculators
Day counts, exact ages, working days and date arithmetic. Each one runs in this page, so the dates you type are not sent to our servers — and none of them need an account.
Why these give a different answer from subtracting in a spreadsheet
Most date mistakes come from three places: whether both endpoints are counted, what a “month” means when months have different lengths, and which days are excluded. Each calculator here states which convention it uses and shows the working — the leap days inside a range, the holidays it removed, the day a clamped month landed on — so the number can be checked rather than trusted.
When counting between two dates, yes — both endpoints are included if they are working days, which is what NETWORKDAYS does in Excel. When adding business days to a date, the start date is not counted, which is what WORKDAY does. The two conventions differ deliberately, and each page section says which it uses.