Free Date Calculator - Add or Subtract Days
Add or subtract days from a date instantly and calculate date differences and timelines.
Formula & Methodology
The Date Calculator measures the span between two calendar dates by converting each date to a day count and taking the difference, which accounts for varying month lengths and leap years automatically. It can also add or subtract an offset in days, weeks, months, or years to a start date to find a target date.
- Days Between = |Date₂ − Date₁| in days
- Target Date = Start Date + Offset (days/weeks/months)
Worked Example
Using the Date Calculator: apply the formula above to your input values. For instance, Days Between = |Date₂ − Date₁| in days, then Target Date = Start Date + Offset (days/weeks/months). The tool performs each step instantly and shows the result.
Frequently Asked Questions
What can this date calculator do?
It finds the number of days between two dates or adds/subtracts days, weeks or months from a start date.
Does it count leap years?
Yes. Calculations account for leap years and varying month lengths so the day counts are accurate.
Does it include or exclude the end date?
The result shows the elapsed span; for working days specifically, use our Business Days Calculator instead.