Date Difference Calculator

Formula

Calendar span = years, months, days (borrowed) · Total days = ⌊(end − start) ÷ 86,400,000⌋

The headline breaks the gap into calendar years, months, and days by borrowing from the prior month when the day count goes negative — the same way you'd count on a wall calendar. Total days is a flat count of midnight-to-midnight boundaries, which can differ slightly from years×365 because of leap years.

Worked example

From 1 January 2024 to 30 August 2026 is 2 years, 7 months, and 29 days — and 972 total days (138 weeks and 6 days). The calendar breakdown and the flat day count both appear because contracts and birthdays use different notions of 'how long'.

Where this can give the wrong answer

• If the end date is before the start date, the calculator swaps them and shows the absolute difference with a note — it won't return a negative span.
• Month lengths vary (28–31 days), so '1 month' from 31 January lands on 28 or 29 February, not '31 days later'.
• Total weeks uses integer division of total days by 7; the remainder days don't account for which weekday you started on.

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