Find the exact number of days between any two dates
Date arithmetic is surprisingly awkward to do in your head. Counting from a date in the past to today, or from today to a future date, requires remembering how many days are in each month, whether the year is a leap year, and carrying across month and year boundaries. This calculator does all of that instantly. Enter two dates and you immediately see the number of days between them, along with the equivalent in weeks and months.
How to use it
Click or tap in the start date field and select a date from the calendar picker, or type it in the format your browser expects. Do the same for the end date. The number of days appears immediately without pressing any button. You can enter the dates in any order — if the start date is later than the end date, the calculator still returns the correct positive count.
Common uses
Counting days between dates comes up constantly in everyday life. How many days until a vacation? How many days since an important event? How long until a deadline? How many days has a plant been growing, a wound healing, or a project running?
In business, date differences are used to calculate invoice due dates, payment terms, contract durations, and project timelines. A 30-day payment term from an invoice dated May 3 ends on June 2. A 90-day trial period starting January 1 ends on April 1 in a non-leap year. Getting these right matters for contracts and compliance.
Legal and financial contexts often require precise day counts. Loan interest is frequently calculated on a daily basis, so the number of days between drawdown and repayment directly affects the interest owed. Regulatory deadlines are often specified in calendar days from a trigger event, and missing them by even one day can have consequences.
The difference between calendar days and business days
This calculator counts calendar days — every day including weekends and public holidays. If you need to count only working days (Monday through Friday, excluding holidays), that is a different calculation. Calendar days are the right measure for most purposes: drug half-lives, age calculations, elapsed time in general, and legal deadlines that say "30 days" without specifying business days.
Weeks and months as alternate units
The calculator also shows the equivalent in weeks and decimal months. Weeks are exact integer divisions of the day count where applicable. The months figure is approximate because months vary in length from 28 to 31 days. For most purposes, "approximately 3.2 months" is a helpful way to understand a 97-day span, but for anything requiring exact month counts consult a calendar directly.
Legal and financial precision
Beyond everyday planning, precise day counts carry real legal and financial weight. A "30-day notice period" written into a lease or employment contract usually means exactly 30 calendar days, and being off by even one day in either direction can affect whether a notice was validly given. Statutes of limitation, cooling-off periods for consumer purchases, and warranty windows are all frequently defined as an exact number of days from a triggering event, and getting the count wrong — whether by forgetting a leap day or miscounting across a month boundary — can have consequences well beyond mere inconvenience. This calculator's day count is exact for any range, however far apart the two dates fall, because it works from the underlying date arithmetic rather than an approximation.
Leap year handling
The calculator uses the standard Gregorian calendar rule for leap years: a year divisible by 4 is a leap year, except for century years, which must also be divisible by 400. This means 2000 was a leap year but 1900 was not. Every February 29 is counted correctly in any date range.
Weeks and months as alternate units, in detail
Beyond the raw day count, the calculator also shows the equivalent span in weeks and in decimal months, since different tasks call for different units. A project timeline is often easier to reason about in weeks — "this sprint is 3 weeks" reads more naturally than "this sprint is 21 days" even though they mean the same thing. The months figure is necessarily approximate, since months vary from 28 to 31 days, so "approximately 3.2 months" for a 97-day span is a useful estimate rather than an exact count; for anything that needs an exact number of calendar months, checking directly against a calendar remains the most reliable approach.
A worked example
Suppose you want to know how many days are left until a deadline on the 15th of next month, from today. Rather than counting on your fingers through the remaining days of this month and adding the days into next month, simply enter today's date as the start and the deadline as the end, and the exact count — correctly handling the different month lengths and any leap year in between — appears immediately. The same approach works equally well looking backward: entering a past date as the start and today as the end tells you precisely how long ago something happened, in days, weeks and months at once.
Private and instant
No data is sent anywhere. The calculation happens entirely in your browser using the JavaScript Date API, the same system used by every modern website and application for date handling, so the result appears instantly and every date you enter is discarded the moment you close or reload the page.
Days between dates FAQ
- Does the calculator include both the start and end dates?
- The result counts the number of days from the start date up to but not including the end date, which is the most common convention for date differences. To include both days, add one to the result.
- Can I calculate days in the past?
- Yes, you can enter any two dates in any order. The calculator always returns the absolute number of days between the two dates.
- What about leap years?
- Leap years are handled automatically. February 29 is a valid date when available and the extra day is counted correctly in any date range spanning a leap year.