Date Calculator
Calculates date differences or adds/subtracts time — business days, ISO week and more.
All date arithmetic (difference, add/subtract, breakdown) runs entirely in your browser, as always. The one exception is the "Consider Brazil's national holidays" option: when checked, the two dates in the range (never anything else) are sent to Nexinon's own public holidays API to find out which dates to exclude — unchecked, nothing leaves the browser.
Date difference and calendar arithmetic
Calculating "how much time is there between two dates" or "what date results from adding N days to another" looks trivial, but hides real calendar decisions — months of different lengths, leap years, what to do when the source day doesn't exist in the target month. This tool solves both operations (they're inverses of each other) on the same screen, under the same two modes: Difference and Add/Subtract.
Inclusive vs. exclusive counting
Between Jan 1st and Jan 3rd there are "2 days" (exclusive — the distance between the two points) or "3 days" (inclusive — also counting the start day itself)? Both answers are correct, depending on what the question actually means (a trip that starts on day 1 and ends on day 3 lasts 3 nights, but the interval between the two points in time is 2 days). This tool exposes both conventions instead of silently picking one — the toggle only appears when time is off, since with time included the difference is already exact by nature.
Adding months/years past month-end (Jan 31 + 1 month)
February doesn't have 31 days — so "Jan 31 + 1 month" can't become "Mar 3" (which is what would happen if the calculation simply "rolled over" the excess into the next month). This tool uses the same convention as Excel/Google Sheets (EDATE) and widely used date libraries: when the source day doesn't exist in the target month, the result falls back to the last valid day of that month (Jan 31 + 1 month = Feb 28, or Feb 29 in a leap year).
Hours/minutes/seconds are exact time — days/weeks/months/years are calendar
With time included, "adding 1 day" and "adding 24 hours" can produce a result that differs by up to 1 hour, on a daylight saving time transition day. Days/weeks/months/years advance by calendar field (always the same wall-clock time, including across a DST region); hours/minutes/seconds advance by exact elapsed time (always precise to the millisecond). Both semantics are intentional — each answers a different question.
Business days: Monday to Friday, holidays optional
By default, business days only considers the fixed calendar (excludes Saturday and Sunday) — no holidays, no network call. Checking "Consider Brazil's national holidays" adds a second number that already excludes the period's national holidays (looked up from Nexinon's own public holidays API); "Also include ponto facultativo days" adds Carnival, Ash Wednesday and Corpus Christi to that exclusion — days that don't bind private employers, but that many companies take anyway. The option only covers Brazil (the only dataset Nexinon maintains today) and only the Difference mode — Add/Subtract has no "business day" unit.
Frequently asked questions
February doesn't have 31 days. Instead of letting the excess "roll over" into the next month (which JavaScript's native date constructor would do on its own), this tool uses the same rule as Excel/Google Sheets: it falls back to the last valid day of the target month. See "Adding months/years past month-end", above.
Inclusive counting adds 1 day to the interval, also counting the end day (e.g., Jan 1st to Jan 3rd becomes 3 days instead of 2). It only shows up without time included — with time, the difference is already exact, with no such ambiguity.
Not by default — business days just means "not a Saturday or Sunday", 100% local. Checking "Consider Brazil's national holidays" adds a second number that also excludes the period's national holidays (and, optionally, ponto facultativo days) — see "Business days", above. Brazil only — the only country Nexinon covers today.
Usually none — but on a daylight saving time transition day, they can differ by 1 hour. "1 day" advances a calendar field (same wall-clock time on the next day); "24 hours" advances an exact elapsed time. See "Hours/minutes/seconds are exact time", above.
No — it's just this page's own URL with the entered values as parameters. It keeps working as long as the tool exists, with no server storing the calculation.
Years/months/days form a single, unambiguous calendar breakdown. "Weeks" shows up as an independent total (how many weeks fit in the whole interval), not as a fourth unit inside that same breakdown — mixing the two would require an extra convention with no clear standard (how many "leftover" days become a week vs. a loose day).
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