Calendar-day differences, business-day counting, days-until questions and date arithmetic. Use the calculators for your own numbers and the guides for formulas, examples and common questions.
Use the tool that matches the exact problem you need to solve.
Add or subtract a chosen number of calendar days from any date.
Calculate age in years, months and days from a birth date to a selected date.
Count the number of calendar days between two dates.
Convert the calendar-day difference between two dates into weeks and remaining days.
Calculate completed calendar months plus remaining days between two dates.
Count weekdays between two dates, excluding Saturdays and Sundays.
Count calendar days from a starting date to a future or past target date.
Find the weekday for any valid calendar date.
11 focused guides and worked examples for this calculator cluster.
Learn how date-difference calculations work and why inclusive versus exclusive counting can change the answer.
Read guide →Dates & DeadlinesLearn how to add or subtract calendar days from a date across month and year boundaries. See formulas, worked examples and related free calculators.
Read guide →Dates & DeadlinesLearn how to count business days between dates, including 3–5 and 7–10 business-day examples, weekends, holidays and inclusive counting.
Read guide →Calendar-day differences, business-day counting, days-until questions and date arithmetic. The pages in this cluster are intentionally connected: calculator pages handle the arithmetic, while the guides answer informational searches, show worked examples and explain how to interpret the result.
Use the examples as reference points, then open a calculator and substitute your own values. For decisions involving contracts, taxes, health, payroll rules, construction requirements or other high-stakes details, verify the real-world assumptions with an appropriate authoritative source.
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