About this date difference calculator
The date difference calculator answers “how many days until…?” and “how long between…?” for project timelines, travel planning, warranties, and legal deadlines.
How to use
- Pick a start date and end date.
- View total days plus an exact years/months/days breakdown.
Formula
Total days use the millisecond difference divided by 86,400,000. The Y/M/D breakdown uses calendar month borrowing, same as the age calculator.
Worked examples
Example: From 1 Jan to 1 Apr in a non-leap year → 90 days.
Tips
- Order of dates does not matter — the span is absolute.
- For business days only, exclude weekends/holidays separately.
Frequently asked questions
Does it include the end date?
The total days value is the full day count between the two midnights (end − start). For inclusive counting of both calendar dates, add 1.