Date Calculator
Add or subtract days, weeks, months, and years from a date, or calculate the duration between two dates.
Start from a date and add or subtract a period of time. Use negative numbers to subtract.
Calculate the number of days between two dates. The start date is excluded from the count.
How to use this tool
- Choose between Add / Subtract mode or Days Between mode.
- For Add / Subtract: enter a start date and the number of years, months, weeks, and days to add. Use negative numbers to subtract.
- For Days Between: enter two dates to find how many days separate them.
- Click Calculate to see the result.
The calculator handles leap years and month boundaries correctly. For example, adding one month to January 31 gives February 28 (or 29 in a leap year), since February doesn't have 31 days.
Frequently asked questions
The count excludes the start date and includes the end date. For example, from January 1 to January 3 = 2 days.
When adding months, if the resulting month has fewer days than the original date, the result is clamped to the last day of that month. For example, January 31 + 1 month = February 28 (or 29 in a leap year).