Date & time
Date difference
Count calendar days and weeks between two dates.
Calculators / Date & time / Date calculator
Date calculator
Add or subtract days, weeks, months, and years from a chosen calendar date.
On this page
Resulting date2026-01-31
Calendar days entered30days
Calendar months entered0months
Calculator controls
How to calculate
Add or subtract days, weeks, months, and years from a chosen calendar date.
Resulting date = starting date ± entered years, months, weeks, and days.
Worked example
Example inputs
Starting date: 2026-01-01 · Operation: Add time · Days: 30 · Weeks: 0 · Months: 0 · Years: 0
Example resultResulting date: 2026-01-31 · Calendar days entered: 30 days · Calendar months entered: 0 months
Assumptions and limits
Uses the Gregorian calendar. When a target month is shorter, the day is clamped to the final valid date of that month.
Results are rounded for display; calculations use unrounded values. Read our calculation methodology.
Understanding the result
Adding zero keeps the starting date. Adding one gives the next calendar day, so the starting date is not counted as day one.
When this tool is useful
Plan a reminder, estimate a calendar milestone or check a date offset.
Understanding your inputs
| Input | What to enter |
|---|---|
| Starting date | Enter the value in the format shown. |
| Operation | Enter one of the available options. |
| Days | Enter a number of at least 0 and no more than 366000. |
| Weeks | Enter a number of at least 0 and no more than 52000. |
| Months | Enter a number of at least 0 and no more than 120000. |
| Years | Enter a number of at least 0 and no more than 1000. |
Frequently asked questions
Are weekends skipped?
No. This tool adds calendar days. Use the business-days calculator to count weekdays within a date range.
Does this calculate a legal deadline?
No. Legal and contractual deadlines can use special rules for counting days, holidays and extensions. Check the applicable rules separately.