Days Between Dates
The days between dates calculator works out how many days and weeks fall between two chosen dates. It also runs the other way – add or subtract any number of days from a start date to find the resulting date. Handy for planning deadlines, calculating notice periods or counting down to an event. Everything runs directly in your browser; no date is ever sent anywhere.
How the days between dates counter works
The tool performs two independent calculations. The first finds the difference between two dates: it takes the "From" date and the "To" date, converts both to the number of milliseconds since the start of time-keeping, and divides the difference by the number of milliseconds in a single day (86,400,000). It rounds the result to whole days and also divides it by seven to show the number of weeks to one decimal place.
The second calculation adds days to a date: it takes the "From" date, adds the entered number of days (which can be negative to subtract) and shows the resulting date in YYYY-MM-DD format. The tool automatically rolls over month ends and leap years correctly, so you never have to worry about how many days a given month has.
The inputs are two calendar dates and one whole number (a day count). The outputs are the number of days, the number of weeks and a new date. On opening, both fields are pre-filled with today's date so you see a result immediately.
How to use the days counter
- Enter the start date in the From field (today's date by default).
- Enter the end date in the To field.
- The number of days and number of weeks between the two dates appear instantly.
- To add days to the "From" date instead, type a day count into the Add to From date field (a positive number adds, a negative one subtracts).
- The resulting date appears just below.
Example – how many days are left until year-end, and what date falls 100 days from the start of August:
| Input | Output |
|---|---|
| From 1 Aug 2026, To 31 Dec 2026 | 152 days (21.7 weeks) |
| From 1 Aug 2026 + 100 days | 2026-11-09 |
| From 1 Jan 2026, To 1 Jan 2027 | 365 days (52.1 weeks) |
What the days counter is good for
The calculator helps whenever you need to work with time spans. Typical scenarios: calculating deadlines and due dates (invoice maturity, notice period, a statutory 14-day window), counting down to an event (a wedding, a holiday, a project deadline), planning recurring intervals, or tracing back the date on which something began. Project managers, accountants, lawyers and students all use it.
Because the whole calculation runs locally in your browser, none of the dates you enter leave your device – nothing is sent to any server. That is useful if you are working with sensitive deadlines, or you simply want a fast answer with no sign-up and no tracking.
FAQ
Is the end day included in the result?
The tool computes the plain difference between dates. The gap between the 1st and the 2nd is 1 day. If you need the end day counted too (an inclusive count), add 1 to the result.
Why do the weeks show a decimal number?
Weeks are the day count divided by seven. For example, 10 days is 1.4 weeks. The decimal shows the partial extra week.
Can I subtract days rather than only add them?
Yes. Enter a negative number in the add-days field, such as -30, and the tool finds the date 30 days before the "From" date.
Does the tool handle leap years?
Yes. The calculation relies on the browser's standard calendar, which accounts for leap years and a 29-day February automatically.
Can I enter dates in the past?
Yes, both fields accept any date. If the "To" date is earlier than "From", the day count will be negative.
Is my data sent to a server anywhere?
No. All calculation runs directly in your browser using JavaScript. The dates you enter never leave your device.
Does it count working days or all days?
It counts all calendar days including weekends and holidays. The tool does not distinguish business days.
What format is the resulting date shown in?
The date produced by adding days is shown in YYYY-MM-DD format (year-month-day), for example 2026-11-09.
Sources & standards
📅 Last updated: 11 July 2026