How are days between dates counted?

By default we count whole calendar days between the two local dates (Jan 1 → Jan 11 = 10 days). Turn on inclusive count to include both endpoints (Jan 1 → Jan 11 = 11 days).

Can I add or subtract days from a date?

Yes. Choose Add days or Subtract days, pick a start date, and enter a whole number of days. Month and year boundaries are handled automatically.

Does this use business days only?

No. Every calendar day counts, including weekends and holidays. Business-day calendars vary by country and employer.

Why not use UTC timestamps?

Date-only inputs are interpreted in your local calendar so the day you pick matches the result. That avoids off-by-one errors common with UTC midnight parsing.

Calculator

Date Calculator

Count calendar days between dates, optionally inclusive, or add and subtract days from any date. Useful for deadlines, leave planning, and schedules—runs locally in your browser.

Date maths

Count days between two dates, or add/subtract days from a start date. Uses your local calendar—no upload.

Start date

End dateInclusive count (count both start and end days)

Result

364 days0 days

Calendar difference. ≈ 52 week(s), 0 day(s).

Useful for

DeadlinesLeave planningTravel nightsSchedules

Age calculatorYears, months, and days from a birth date.

Days untilHow many days remain until a target date.

Week numberISO week number for any calendar date.

Privacy & limitations

v1.0.0·Updated 2026-09-25

Files are processed in your browser and are not uploaded to our servers.

Your files stay on your device. We do not store or access your documents.

Guides, tips & FAQ

What is a calendar day difference?

A calendar-day difference counts midnights crossed between two local dates. It ignores clock time. Inclusive counting adds one so that a single-day event from Monday to Monday counts as one day.

How days are counted

days = calendar_date(end) − calendar_date(start)

Inclusive days = |days| + 1. Add/subtract uses whole-day steps on the local calendar (month and year boundaries included).

Worked example

Leave from 1 Jan 2026 to 11 Jan 2026.
Difference = 10 days (exclusive end), or 11 days inclusive.
10 days ≈ 1 week and 3 days.
10 days between (11 inclusive)

Common uses

Project deadlines and notice periods
Travel duration and hotel night estimates (check inclusive rules)
Exam prep schedules — add N days from today
Pair with the age calculator for Y/M/D age instead of raw days

Related tools

Need years/months/days from a birth date? Use the age calculator. Terms like leap year are covered in the glossary.

Frequently asked questions

Date maths

Related calculators

Guides, tips & FAQ

Frequently Asked Questions