Date Calculator

Add, subtract, or compare dates.

Calculate an offset from one date or compare two dates with calendar-day, full-week, and weekday results.

ResultOffset

How it works

Offset mode moves a date by whole days, weeks, months, or years. Difference mode measures the absolute interval and reports its direction, calendar days, full weeks with remaining days, and Monday-to-Friday weekdays.

Choose an offset calculation or compare two dates. All calculations use date-only UTC values.

Practical examples

  • Adding 30 days to 2026-07-21 returns 2026-08-20.
  • Adding one day to Friday 2026-07-24 with weekend skipping enabled returns Monday 2026-07-27.
  • Comparing Friday 2026-07-24 with Monday 2026-07-27 returns 3 calendar days and 1 weekday.

How to read the result

  • Offset results show an ISO date in YYYY-MM-DD format and its weekday.
  • Date differences exclude the start and include the end by default; the inclusive option counts both dates.
  • Difference results show direction, calendar days, full weeks plus remaining days, and Monday-to-Friday weekdays.

Limits and privacy notes

  • Adding months or years uses calendar arithmetic, so dates near a month end can roll into the following month.
  • Weekday calculations exclude Saturday and Sunday but do not know regional public holidays.
  • Date values are processed locally in your browser and are not uploaded.

Method used

  • Dates are parsed as UTC calendar values so daylight-saving changes and local time zones do not alter day counts.
  • Day and week offsets change the calendar date by 1 or 7 days per unit; weekend-skipping offsets count Monday through Friday.
  • Date differences use the absolute interval while the direction line reports whether the end is before, after, or equal to the start.

Sources and standards

Two modes

Offset or compare

  • Use Add/subtract offset to move from one date.
  • Use Difference between two dates to measure an interval.
  • The visible fields follow the selected mode.
Counting rule

Know which dates count

  • Standard differences exclude the start and include the end.
  • Inclusive mode counts both endpoints.
  • Reversing dates changes direction, not the absolute interval.
Weekday scope

Monday through Friday

  • Skip weekends for working-day offset estimates.
  • Difference mode reports weekdays separately.
  • Public holidays require a separate calendar check.

Frequently asked questions

Do weekday calculations include public holidays?

No. Offset and difference modes exclude Saturdays and Sundays only; regional and company holidays need a separate calendar check.

Does the date difference include both dates?

Not by default. The standard result excludes the start and includes the end. Enable Include both start and end dates to count both endpoints.

Why can adding one month move into another month?

Calendar months have different lengths. Browser date arithmetic normalizes dates that do not exist in the target month.

Can I enter a negative offset?

No. Enter a whole number of units and choose Add or Subtract to control the direction.

Why does reversing the two dates keep the same day count?

The calculator reports an absolute interval and uses a separate direction line to show which date comes first.

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