Reference formulas and worked examples below keep their stated units. Monetary examples use USD; dimensional examples use US customary units unless labeled otherwise. Metric calculator inputs are converted to these reference units before calculation. Choosing another currency does not convert example amounts or exchange money.
How to use this date calculator
Choose days between dates, add time, or subtract time. Calendar days include weekends and holidays.
How the calculation works
Elapsed days = end date − start date, calculated as a date-only difference. Including the end date adds one day so both endpoints are counted.
To add or subtract time, first combine years and months into one calendar-month shift, clamping a missing day to the destination month end. Then apply weeks × 7 plus days. For example, January 31 plus one month becomes February 28 in a non-leap year.
Full weeks = whole days ÷ 7 rounded down. Remaining days are what is left after those full weeks.
Worked example
September 22 to December 25, 2026 is 94 elapsed days, or 13 weeks and 3 days. Count both dates for 95 days. Adding 30 days to September 22 gives October 22, 2026.
Limits and assumptions
Counts all calendar days, including weekends and holidays. It does not calculate business days. Supported input and output dates are in years 1000–9999.
Frequently asked questions
Are weekends excluded?
No. This calculator counts calendar days.
What happens when both dates are the same?
Elapsed days are zero. With inclusive counting, the result is one day.
Does daylight saving time change the answer?
No. These are date-only calculations, independent of clock changes.