Days Between Dates Calculator
Count elapsed calendar days between two dates.
Formula
- Use the units shown beside each field.
- Results update automatically whenever you change an input.
- Displayed values use up to four decimal places, or scientific notation for very small or large numbers. Calculations use standard floating-point arithmetic; exact integer and fraction tools identify their own precision rules.
- The start day is excluded. Negative values mean the end date precedes the start.
Example Calculation
- Start date: 2026-01-01
- End date: 2026-02-01
From 1 January 2026 to 1 February 2026 there are 31 elapsed days.
Frequently asked questions
How do I use this calculator?
Enter start date, end date. The result updates automatically. Use Reset to restore the example values.
What method does it use?
Days = (UTC end date − UTC start date) / 86,400,000. The start day is excluded. Negative values mean the end date precedes the start.
Why might a rounded result differ?
The calculation keeps full numeric precision internally, then rounds the displayed result. Rounding intermediate steps by hand can produce a slightly different answer.
Are my inputs saved online?
No. This calculator processes your inputs in your browser. A recently used list stores only calculator names on this device, not your entered values.
Check the assumptions and units before using this result. Read about calculation methods.