Three simple steps
How to use the Date Calculator
- 01
Choose a starting calendar date.
- 02
Select add or subtract, then enter the time units.
- 03
Read the resulting ISO date and full weekday name.
Everyday date tool
Date Calculator
Move forward or backward from any date using a combination of years, months, weeks and days.
Instant calculation Runs in your browser
Resulting date
2026-08-15Saturday, 15 August 2026
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Worked example
Add 10 days to 5 August 2026
Calculation5 August 2026 + 10 calendar days
Result15 August 2026
The method
How it works
Calendar order
Years and months are applied first, followed by the combined number of weeks and days.
Real month lengths
The browser calendar handles different month lengths and leap years instead of treating every month as a fixed number of days.
Local-time safe
Dates are calculated as UTC calendar values to avoid daylight-saving changes shifting the displayed day.
Helpful answers
Frequently asked questions
Are weekends included?
Yes. This tool adds calendar time. Use Days Between Dates for a separate weekday count.
How are months handled?
Months follow normal calendar rollover rules, so moving from a date near month-end may roll into the following month.
Does it account for leap years?
Yes. The calculation uses real calendar dates, including February 29 in leap years.