Date calculator for adding or subtracting days, weeks, months, and years. Choose a starting date or compare two dates to find the interval.
The Date Calculator lets you add or subtract days, weeks, months, and years from a starting date. Use the date difference calculator to compare two dates instead of counting the days by hand.
Choose add/subtract mode to find a future or past date. In difference mode, enter two dates to find the interval between them. Check the result against the date convention your task requires.
Find the date 90 days after a project kickoff:
2026-01-1590 days2026-04-15The interval crosses January, February (28 days in 2026), March, and April.
Decide whether your task includes the start date. A "30-day" period can have different end dates depending on that convention. Compare the interval in difference mode to check your count.
Months have different lengths, so adding months is not the same as adding a fixed number of days. When a date such as January 31st falls beyond the end of the target month, check how the calculator handles the result. For legal or contractual deadlines, also check whether weekends and holidays count.
Use the month or year inputs in add/subtract mode. Review the resulting date when the interval crosses a leap day or the end of a month.
Choose difference mode and enter the start and end dates. Read the interval, then check whether it matches the counting convention you need.
Use the subtract option to move backward from the starting date.
Check the interval before relying on it for a deadline. Keep the same start-date convention throughout your calculation.
For a separate arithmetic task, use the Factorial Calculator.
How to Use Date Calculator - Add or Subtract Days
Use add/subtract mode to move from a starting date, or difference mode to compare two dates.
For add/subtract mode, choose the start date and enter the days, weeks, months, or years. For difference mode, enter both dates.
Read the resulting date or interval. Check how the start date, month ends, weekends, and holidays should count for your task.
Date calculator for adding or subtracting days, weeks, months, and years. Choose a starting date or compare two dates to find the interval.
Tool Use:
15Added:
Sep 11, 2026Type:
Free ToolPrivacy:
Client SideCompare today or another selected date in common formats and check a custom pattern before copying.
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