Add or Subtract Days
Add or subtract days, business days, weeks, months or years from a date to find a deadline or due date.
Adding months at the end of a month
Months and years are added to the calendar date. When the same day does not exist in the resulting month, the last day of that month is used: 31 January plus one month is 28 February (29 February in leap years), and 29 February plus one year is 28 February. Days and weeks are always exact counts of 24-hour calendar days.
Frequently asked questions about adding days
Is the start date counted?
No. Adding 1 day to Monday gives Tuesday. For business days the count also starts on the day after the start date.
What is 90 days from today?
Leave the start date blank, choose Add, type 90 and choose Days. The result shows the date and its weekday.
Why does adding one month to 31 January give 28 February?
February has no 31st day, so the date moves to the last day of February. The same rule applies to any month that is shorter than the start month.
Which holidays are skipped in business days?
The national public holidays of the chosen country and, when you pick one, the holidays of the state or region. Weekends follow the country (Friday and Saturday in Saudi Arabia).
How the add or subtract days calculator works
This calculator adds or subtracts days, business days, weeks, months or years from any date. Leave the start date blank and it uses today, so you can find out in one click what the date will be 90 days from now or what it was 30 days ago. Typical uses are payment and delivery deadlines, due dates, notice periods, contract end dates, warranty expirations, trial periods and project milestones. It is useful for anyone who plans around dates: freelancers, students, managers, accountants and travellers. The result shows the new date with its weekday and the number of calendar days between the two dates.
The calculation follows the ISO calendar used by Java: days and weeks are exact counts of calendar days, while months and years keep the day of the month and, when that day does not exist in the target month, move back to the last valid day of that month. The start day itself is never counted, so adding 1 day to Monday gives Tuesday. The business days option skips weekends and the public holidays of 68 countries and their regions, using the same calendars as the Business Days Calculator, for the years 1990 to 2100. Weekends follow each country, for example Friday and Saturday in Saudi Arabia.
Example: 24 October 2026 plus 90 days is Friday 22 January 2027, and 31 January 2026 plus 1 month is Saturday 28 February 2026, because February has no 31st day. For business days, 17 April 2026 plus 5 business days in Brazil is Monday 27 April 2026: the weekend of 18 and 19 April and the Tiradentes holiday on Tuesday 21 April are skipped. Limitations: municipal holidays and the days off of a single company are not included, and legal deadlines may follow their own counting rules, so check them against the rules that apply to your case.