Date Calculator
Days between two dates, or add and subtract days from one.
About the date calculator
Two calculators in one. Difference counts the gap between two dates β in days, in years, months and days, and split into weekdays versus weekend days. Add / subtract moves a date forward or backward by a number of days, weeks, months or years.
The weekday split is the part most date calculators leave out, and it is usually the number you need: delivery estimates, notice periods, contractual deadlines and project plans are nearly always counted in working days.
Month arithmetic and the clamping rule
Adding a month to 31 January has no obvious answer, because February has no 31st. The convention used here β and by most spreadsheet and database software β is to clamp to the last valid day of the target month, so 31 January plus one month is 28 or 29 February.
The consequence is that month arithmetic is not always reversible: 31 January plus one month is 28 February, but 28 February minus one month is 28 January. That is expected behaviour rather than a bug, and it is worth knowing about when a contract counts in months rather than days.
Frequently asked questions
How many days are between two dates?
Enter both dates in the Difference tab. The headline figure is the total number of days, with a years-months-days breakdown underneath and the weekday and weekend split beside it.
How do I count only working days?
The "Weekdays" figure counts Monday to Friday across the range and excludes Saturdays and Sundays. Note that it does not know about public holidays, which vary by country, so subtract those yourself.
How do I add 90 days to a date?
Use the Add / subtract tab: enter the starting date, set the amount to 90, choose "days" and "after". The resulting date is shown with its day of the week.
Does the calculator include both the start and end date?
The day count is the gap between the dates, so it excludes the end date. From 1 January to 8 January is 7 days. If your situation counts both endpoints, add one.
How does it handle leap years?
Automatically. A range spanning 29 February includes that day in the count, which is why 2024 to 2025 gives 366 days while 2023 to 2024 gives 365.