Days between dates
Pick two dates. Leap years and month lengths are handled, and the weekday count comes free.
Counting days is harder than it looks
Months are 28, 29, 30 or 31 days, and February changes with a rule that skips centuries not divisible by 400. Any mental shortcut based on 30-day months drifts within a few weeks, which is why date arithmetic is worth calculating rather than estimating.
The weekday figure counts only Monday to Friday between the two dates, which is what you want for lead times, notice periods and delivery estimates. It does not know about public holidays — those are regional, and the business days calculator on this site lets you subtract them explicitly.
The whole-months figure counts complete calendar months rather than dividing days by thirty, so from the 15th of one month to the 15th of the next is exactly one month regardless of how many days that month happened to have.
Questions
Is the end date included?
No — this counts the days between, so the 1st to the 3rd is two days. If you need the count including both endpoints, add one; the business days calculator counts inclusively instead.
Does it handle leap years?
Yes. The calculation uses real calendar dates, so 29 February and the century rule are both handled correctly.
Can I count backwards?
Yes — put the later date first and the result shows the same gap, with a note that the second date is earlier.