Date Duration Calculator
Count days, weeks and months between any two dates — or count down to an event, with an optional business-days mode.
Calculate
Tip: leave the end date as today to count down to an event.
How to Use the Calculator
Days between counts the calendar days from a start date to an end date — order doesn't matter, and leap days count automatically. Tick business days to count Monday–Friday only (handy for deadlines and SLAs). Add / subtract days jumps forward or backward from any date: enter −45 to go back 45 days. Leave the end date as today and the page becomes a live countdown to your event.
How Date Math Works
Dates are counted on the real Gregorian calendar — not "30 days per month" averages. The difference between two dates is simply:
January 1 → October 30, 2026: Jan 31 + Feb 28 + Mar 31 + Apr 30 + May 31 + Jun 30 + Jul 31 + Aug 31 + Sep 30 = 273 days, plus 29 days of October = 302 days. The convention here: the count excludes the start day and includes the end day — so "7 days from Monday" lands on the following Monday.
Worked Example
Project kickoff Jan 1 → launch Oct 30, 2026
Calendar days: 302.
Weeks: 302 ÷ 7 = 43.1.
Calendar breakdown: 9 months, 29 days.
Business days: about 216 (302 days minus ~86 weekend days) — the calculator counts them exactly, skipping Saturdays and Sundays.
Countdown Mode: Days Until an Event
Set start = today, end = your event. Weddings, launches, exams, vacations — the number updates every time you open the page. Psychologically, countdowns work: a visible "47 days left" focuses effort better than a distant date. For long countdowns, the weeks/months figures help ("about 6.7 weeks"), and for deadlines the business-day count tells you how many working days you actually have.
Business Days Option
Business days = Monday through Friday, excluding weekends. A "10 business day" turnaround starting Monday the 1st lands on Monday the 15th — two full weeks later, which surprises people expecting "10 days = next Thursday." Two caveats: public holidays aren't excluded (they vary by country and region — subtract them manually), and some industries count Saturday as a business day. When a contract says "business days," always check whose definition applies.
My saved numbers reuse them in any calculator
Save a number once — like your rent or hourly rate — then just type its name instead of the number, in any calculator here. You can also type formulas like 5000 * 1.1 right into any box.
Saved only in this browser — nothing is sent to us.
Frequently Asked Questions
How many days are between two dates?
Subtract the earlier date from the later one on a real calendar, counting leap days. January 1 to October 30, 2026 is 302 days. Enter your dates above for the exact count.
How do I count down to a date?
Set the start date to today and the end date to your event — the calculator shows days, weeks and months remaining. Bookmark the page and it recounts every visit.
Do leap years count in date math?
Yes — February 29 exists on the calendar, so it counts like any other day. Date ranges spanning leap years automatically include the extra day.
Business days vs calendar days?
Calendar days count every day; business days count Monday–Friday only. A "10 business day" deadline starting Monday lands two Fridays later. Note: public holidays are not excluded here — add those manually.
How do I add days to a date?
Use Add/Subtract mode: enter a start date and a number of days to jump forward (or backward with a negative number). Useful for deadlines, billing cycles and travel planning.