Date Calculator
Days between dates, plus adding or subtracting time.
About this tool
Find the number of days, weeks, months and years between two dates — or add a duration to a date to find a future date. Perfect for deadlines, billing and planning.
How it works
The duration mode computes exact year/month/day breakdowns using calendar arithmetic, plus total days via UTC timestamps. The add/subtract mode applies a duration to a start date, normalising month overflow (e.g. Jan 31 + 1 month = Feb 28).
How to use Date Calculator
- 1Choose "Duration between dates" or "Add to a date".
- 2Pick your two dates, or a start date plus days/weeks/months.
- 3Read the result in days, weeks, months and years.
- 4Copy the result for your notes or calendar.
Examples
From 1 January to 1 March is 59 days (60 in a leap year).
Adding 90 days to 15 June 2026 gives 13 September 2026.
A project spanning 6 months and 14 days is about 197 days.
Pro tips
- Use "include end day" when counting inclusive ranges like day 1 to day 5 = 5 days.
- For billing cycles, calendar months can be more relevant than exact days.
- The result shows multiple units so you can pick the format you need.
Frequently asked questions
Does the difference include the end date?
By default it counts full days between the dates (end minus start). An "inclusive" toggle counts the end day too.
How are months counted?
Calendar months: from the 15th of one month to the 15th of the next is exactly 1 month. Day counts also report total days so both views are covered.
Are leap years handled?
Yes. February 29 exists in leap years and is counted correctly.
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