Measure elapsed time between calendar dates
This calculator provides several views of the same interval: total elapsed days, complete weeks plus leftover days, a calendar-style years/months/days breakdown, and a weekday count that includes Monday through Friday.
Formula
total days = (endUTC − startUTC) ÷ 86,400,000Using UTC-normalized date values prevents daylight-saving transitions from turning a date-only interval into 23- or 25-hour days. When inclusive counting is enabled, one day is added so both boundary dates are counted.
Calendar years, months and days
The calendar breakdown is not just total days divided by 365 or 30. The calculator subtracts calendar fields and borrows the actual number of days in the preceding month when necessary. That makes the result more natural for birthdays, contracts and date planning.
Worked example
January 1 to January 31 is 30 elapsed days in the default exclusive mode. Enabling inclusive counting makes it 31 calendar days. The weekday total ignores Saturdays and Sundays but does not know about public holidays.
Assumptions and limitations
Dates must be entered in chronological order. Weekday counting treats Monday through Friday as weekdays everywhere and does not apply national holidays, business calendars, time zones or times of day.
Frequently asked questions
Does the calculator include the end date?
By default it measures elapsed time, so the end date is not counted as an additional day. Enable “Include end date” for inclusive calendar counting.
How are weeks calculated?
The total day count is divided into complete seven-day weeks plus the remaining days.
What does the weekday count include?
Weekdays counts Monday through Friday and excludes Saturdays and Sundays. Public holidays are not removed.
Why can calendar months differ from dividing days by 30?
Calendar months have different lengths. The years/months/days result borrows from real calendar month lengths rather than assuming every month has 30 days.
Are daylight-saving changes a problem?
No. Date-only calculations are normalized to UTC midnight equivalents so daylight-saving clock changes do not add or remove a day.