Date & time · Calendar math
Move dates without losing a day.
Find the gap between two dates, or add and subtract years, months, weeks and days.
Date math
Find the gap between dates or move a date forward and back.
Use negative numbers to subtract. Months are clamped to the last valid day, so January 31 plus one month becomes February 28 or 29.
Choose both dates to compare.
Business days count Monday to Friday and exclude public holidays.
Good to know
The result is a guide, not a guarantee.
This calculator runs entirely in your browser. Check the assumptions, keep the inputs realistic, and use the result as a starting point for a decision.
Calendar arithmetic with month-end clamping. Public holidays and local time zones are not included.
How are business days counted?
Business days include Monday to Friday and exclude the end date. Public holidays are not removed because they vary by country and region.
Why does a month calculation look different from 30 days?
Calendar months have 28–31 days. The calculator steps through real calendar months and clamps to the last valid day, so January 31 plus one month becomes February 28 or 29.
Can I subtract time?
Yes. Use negative years, months, weeks or days in the add or subtract mode. For example, enter -30 days to move back a month.
Does the difference include both dates?
The day count is the gap between the dates, not an inclusive count. January 1 to January 2 is one day. Add one day if you need to count both ends.