Add or Subtract Days from a Date
This calculator adds or subtracts a period — days, weeks, months, or years — from a starting date and shows you the resulting date. It is handy for finding a due date, a deadline, a delivery date, a warranty expiry, or any point a fixed amount of time before or after a known date. Along with the final date, it tells you which day of the week it falls on and the total number of days added or removed.
Resulting date
Day of the week
Difference in days
When adding or subtracting months and years, if the day does not exist in the target month (for example, the 31st in a 30-day month) the result is adjusted to the last day of that month.
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How it works
For days and weeks the calculation is straightforward: the requested number of days (weeks are multiplied by seven) is added to or subtracted from the start date on the calendar. For months and years the calculator moves the month or year and keeps the same day number, unless that day does not exist in the target month — for instance adding one month to January 31 lands on the last day of February, since February has no 31st. This "clamp to end of month" rule is the standard behaviour and prevents the date from spilling over into the following month. Weekends and holidays are not skipped; every calendar day counts.
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Preguntas frecuentes
- What happens when I add a month to the 31st?
- If the target month does not have a 31st, the result is clamped to the last valid day of that month. For example, January 31 plus one month becomes February 28 (or February 29 in a leap year). This is the standard convention and keeps the result inside the intended month instead of rolling into the next one.
- Are weekends and holidays skipped?
- No. This calculator counts every calendar day, including Saturdays, Sundays, and public holidays. If you need to add only working days, use a business-day calculation instead — the two give different results whenever the span crosses a weekend.
- Can I subtract time to find a date in the past?
- Yes. Switch the operation to "subtract" and the calculator moves backwards from the start date by the amount you enter. This is useful for questions like "what date was 90 days ago" or "which day was six months before this appointment".
- How is the day of the week determined?
- Once the resulting date is known, the calculator reads its weekday directly from the calendar and displays it in your language. Because the computation is based on real dates, the weekday is always correct, including across leap years and century boundaries.
- What is the difference between adding 30 days and adding 1 month?
- Adding 30 days always moves exactly 30 calendar days forward, regardless of the month. Adding 1 month moves to the same day number in the next month, which may be 28, 29, 30, or 31 days later. For most months they differ, so pick the unit that matches what you actually mean.