Calendar Calculator
Find the exact number of days between two dates, add or subtract days from any date, or work out an exact age in years, months and days — free, instant and accurate for any year, including leap years.
What Do You Want to Work Out?
Pick a tab below — calculate the gap between two dates, project a date forward or backward, or find someone’s exact age down to the day.
Days Between Two Dates
Enter a start and end date to see the full breakdown
Adds one extra day, useful for counting stays or event lengths inclusively.
Excludes Saturdays and Sundays from a second total. Public holidays are not excluded.
Date Difference Result
Total days plus a years / months / weeks breakdown
Choose a start and end date, then click Calculate Days Between to see the full breakdown.
Add or Subtract Days
Project a date forward or backward from a starting point
Enter any whole number of days to add to or subtract from the start date.
Resulting Date
The calendar date after your adjustment
Choose a start date and number of days, then click Calculate Resulting Date.
Exact Age Calculator
Find an exact age in years, months and days
Leave “Age As Of” as today’s date, or pick another date to see the age on that day.
Age Result
Years, months, days and days until next birthday
Enter a date of birth, then click Calculate Exact Age to see the full breakdown.
Calendar Facts
Handy reference figures used behind the scenes in every calculation on this page.
| Item | Value | Notes |
|---|---|---|
| Days in a common year | 365 | Standard calendar year |
| Days in a leap year | 366 | Includes 29 February |
| Leap year rule | Divisible by 4 | Except century years not divisible by 400 |
| Weeks in a year | 52.14 | 365 ÷ 7, approximately |
| Next leap years | 2028, 2032, 2036 | Every 4 years, with century exceptions |
| Business days per week | 5 | Monday to Friday, excludes weekends |
Calendar Calculator FAQ
Everything you need to know about counting, adding and comparing dates.
It counts the number of calendar days between your start date and end date. If you tick the option to include the end date, that final day is counted too; otherwise the calculator returns the number of full days that have passed between the two dates.
Yes. The Date Difference tab has a business days option that removes Saturdays and Sundays from the total, giving you the number of weekdays between the two dates. Public holidays are not automatically excluded since these vary by country.
Open the Add/Subtract Days tab, pick your starting date, enter the number of days, and choose whether to add or subtract. The calculator returns the resulting calendar date along with the day of the week it falls on.
The Age Calculator compares your date of birth against a chosen reference date, usually today. It counts complete years first, then the remaining complete months, then any leftover days, accounting for varying month lengths and leap years.
Yes. All calculations use native calendar date arithmetic, so leap years such as 2028 and 2032, and February’s 29th day in those years, are automatically factored into every result.