Date Difference Calculator
Find the exact number of days, weeks, months and years between two dates.
How the date difference is calculated
This calculator finds the exact difference between two calendar dates and returns the answer in several units at once: total days, weeks, calendar months, calendar years, plus the equivalent hours, minutes and seconds. Dates are parsed in UTC, so the result stays consistent regardless of your local timezone or daylight saving time — a range from 1 March to 15 March is always 14 days, whether or not a clock change falls inside it. Months and years are counted the way you'd count them on a calendar (so 15 January to 15 March is exactly 2 months), not by dividing the total day count by an average month length.
This calendar-day count is different from a business-day count — a calendar-day span of 14 days (this calculator's default) includes 4 weekend days on a typical two-week stretch, leaving only 10 weekdays inside it. If you need working days specifically — for a deadline, delivery estimate, or payroll window — use the Business Days calculator, which also excludes public holidays. For a running countdown to a specific future date rather than the gap between two fixed dates, see the Countdown calculator.
Frequently asked questions
- What counts as a day in this calculator?
- Each calendar day between the two dates, calculated in UTC so the result never shifts with daylight saving time or your local timezone.
- Does the order of the two dates matter?
- No. Enter them in either order — the calculator always returns the absolute difference.
- Can I use this in my own app?
- Yes — every calculator on Stupidly Clever has a matching REST API and MCP tool that runs the same underlying logic.
- Is there a limit to how far apart the dates can be?
- No practical limit — the calculator works across any range of calendar dates.
- Why do months and years look different from just dividing the days?
- Calendar months are not equal lengths (28–31 days) and years vary (leap years). The calculator computes complete calendar months and years directly rather than dividing total days — so 31 January to 28 February is 1 complete month, even though it's only 28 days.
- What is the difference between calendar days and business days?
- Calendar days count every day including weekends and holidays. Business days exclude weekends and optionally public holidays. Use the Business Days Calculator if you need to count working days between two dates.