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.
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.
Add or subtract a chosen number of calendar days from any date.
Count calendar days from a starting date to a future or past target date.
Find the weekday for any valid calendar date.
Calculate age in years, months and days from a birth date to a selected date.
Three long-tail answers that explain formulas and common scenarios behind this calculator cluster.
Learn how to count business days between two dates, how weekends and holidays affect the answer, and when inclusive or exclusive counting changes the result.
Read guide →Dates & DeadlinesLearn 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.
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.
Continue into another connected area of the reference library.