About Date Calculator
Date calculator to find the number of days, weeks, months, and years between two dates. Free tool to add or subtract days — find deadlines and durations instantly.
How to use
- Choose your calculation mode: find the number of days between two dates, or add/subtract days from a date to find a future or past date. Both modes are useful for deadline tracking, project planning, contract terms, and age calculations.
- Enter your dates using the date picker or by typing directly. The calculator accepts dates in multiple formats and supports dates across centuries for historical calculations. Select whether to include or exclude the start date in the count (some legal and business contexts count differently).
- View the result in multiple time units: total days, weeks, months, and years between the two dates. The breakdown shows each unit precisely — for example, 397 days is 1 year, 1 month, and 1 day, or 56 weeks and 5 days.
- Toggle the business days option to exclude weekends from the count. Business day calculations are essential for contract deadlines (Net 30 means 30 calendar days, but some contracts specify 30 business days), legal notice periods, and project timelines that only count working days.
- Use the add/subtract mode for deadline planning: your mortgage closes in 45 business days from April 1, when is the closing date? A 90-day return policy started on March 15, when does it expire? Your lease began on June 1 for 18 months, when does it end?
- Factor in holidays for the most accurate business day calculations. Standard Canadian statutory holidays are built in, and you can add provincial holidays and company-specific closures for precise deadline tracking.
Examples
Net 30 invoice deadline
Invoice issued April 8, 2026, with Net 30 terms. Add 30 calendar days: payment due May 8, 2026. If the contract specifies 30 business days instead, the due date shifts to May 20, 2026 (excluding 8 weekend days from the count).
Days lived since birthday
Someone born July 15, 1990 calculating their age on April 30, 2026. The result: 35 years, 9 months, 15 days, or 13,074 total days. This includes nine February 29 leap days encountered (1992, 1996, 2000, 2004, 2008, 2012, 2016, 2020, 2024).
Project deadline planning
Project starts April 30, 2026 with a 90-business-day delivery commitment. Adding 90 business days (excluding weekends and Canadian statutory holidays like Victoria Day and Canada Day) gives a deadline of September 8, 2026 — a useful sanity check before signing the contract.
Frequently asked questions
How many days are between two dates?
Count the days from the start date to the end date, with the convention that the start date is day zero and the end date is counted. January 1 to January 31 is 30 days (not 31, because January 1 is the starting point, not a counted day). This calculator handles the counting convention automatically and shows results in days, weeks, months, and years. It correctly accounts for varying month lengths (28-31 days), leap years (February has 29 days every 4 years, except century years not divisible by 400), and date boundaries.
How do I calculate business days between two dates?
Business days exclude Saturdays and Sundays. Between Monday January 6 and Friday January 17 there are 10 business days but 12 calendar days. To calculate manually: count total calendar days, subtract the number of complete weeks x 2 (for weekends), then adjust for partial weeks. This calculator does it automatically and can also exclude statutory holidays. Business day calculations matter for: legal notice periods, contract fulfillment deadlines, shipping estimates, employee probation periods, and financial settlement dates.
How many weeks are in a year?
A standard year has 52 weeks and 1 day (365 days / 7 = 52.143 weeks). A leap year has 52 weeks and 2 days. This means a date falls on the same day of the week the following year except after a leap year, when it shifts by two days. For practical purposes: 52 weekly paychecks per year, 26 bi-weekly paychecks, and 12 monthly paychecks. Some years have 53 pay periods for weekly or bi-weekly pay schedules depending on which day of the week January 1 falls on.
How do I calculate my exact age?
Enter your birth date as the start date and today as the end date. The calculator shows your exact age in years, months, and days. For example, if you were born on July 15, 1990, and today is April 8, 2026, you are 35 years, 8 months, and 24 days old, or approximately 13,050 days old. Exact age calculations matter for retirement eligibility (CPP starts as early as age 60), OAS eligibility (age 65), insurance quotes, and milestone celebrations.
What is a leap year and how does it affect date calculations?
A leap year occurs every 4 years, adding February 29 to the calendar. The rule: divisible by 4 = leap year, except years divisible by 100, unless also divisible by 400. So 2024 is a leap year, 2100 is not, and 2000 was. Leap years affect date calculations by adding one extra day: 365 days between March 1, 2023 and March 1, 2024 versus 366 days between March 1, 2024 and March 1, 2025 (since February 29, 2024 is included). This calculator handles leap years automatically in all calculations.
How do I count days for a contract deadline?
Read the contract carefully: calendar days means every day counts, business days excludes weekends (and sometimes holidays), and banking days typically excludes weekends and bank holidays. Net 30 usually means 30 calendar days from the invoice date. A 90-day probation period starting March 1 ends May 30 (calendar days) or around June 20 (business days). When in doubt, use calendar days as the default interpretation unless the contract specifies otherwise. Legal notice periods in Canada are typically counted in calendar days unless stated as business days. For calculating how many hours fall within a contract period or tracking time against a deadline, pair this with the
Time Duration Calculator.
Can this calculator handle dates in the past?
Yes, the calculator works for any date range: past, present, or future. Calculate how many days since a historical event, find the day of the week for a past date, or determine durations between any two dates in history. The calculator correctly handles the Gregorian calendar, including leap year rules, varying month lengths, and century boundaries. Common historical calculations: days since your company was founded, time elapsed since a warranty start date, or the number of days between two events for insurance or legal claims.
Part of ToolFluency’s library of free online tools for Calculators. No account needed, no data leaves your device.