Date Calculator
Add or subtract days, weeks, months, years or business days from a date, or count the days between two dates.
Result…
How it's calculated
Result = start + n days (weeks × 7; months and years on the calendar) Days between = end − start
Adds or subtracts time on the calendar, or counts the days from one date to another. Days between leaves out the end date, the way most deadlines are counted; "counting both ends" adds it back. Business days skip weekends but not public holidays, which differ by country.
Your numbers, step by step
About the Date calculator
This date calculator does two jobs. It adds or subtracts days, weeks, months, years or business days from a date, and it counts the days between two dates. Use it for deadlines, notice periods, warranties, project schedules and countdowns. When you count between two dates it gives the calendar days, the same span in weeks and in years, months and days, the number of business days, and the total counting both the start and end dates. Months and years are added on the calendar, so one month after 31 January lands on 28 February in a non-leap year. Business days skip weekends but not public holidays, which differ by country. To find someone's exact age, use the age calculator.
How to use it
- Choose what to “Work out”: Add / subtract, or Days between.
- For adding or subtracting, set the “Start date”, the “Direction”, the “Amount” and the “Unit” (days, weeks, months, years or business days).
- For days between, set the “Start date” and the “End date”.
- Read the result date and its weekday, or the days between with the business-day and both-ends counts.
Worked example
90 days after 1 January 2026 is Wednesday 1 April 2026. From 1 January to 25 December 2026 is 358 days, 51 weeks and 1 day, of which 256 are business days (Monday to Friday); counting both the start and the end date gives 359.
Updated
Questions people ask
How do I count the days between two dates?
Choose Days between and enter both dates. The main answer leaves out the end date, the way most deadlines are counted; the “Counting both ends” figure adds it back.
How do I add business days to a date?
Choose Add / subtract and set the unit to Business days (Mon–Fri). Five business days after Monday 12 October 2026 is Monday 19 October 2026.
Does it skip public holidays?
No. Business days skip Saturdays and Sundays only, because public holidays differ by country and state. Subtract any holidays that fall in the period yourself.
What happens when I add a month to 31 January?
The calculator moves on the calendar and lands on the last day of the shorter month, so 31 January 2026 plus one month is 28 February 2026.
Can I count backwards from a date?
Yes. Set the Direction to Subtract. Two weeks before 1 March 2026 is Sunday 15 February 2026.