Finding a Date in the Future or the Past
Deadlines are often expressed as a period rather than a date: "within 30 days", "a 90-day trial", "six weeks from today", "two years after purchase". Turning that into a calendar date means counting across months of different lengths and sometimes skipping weekends. This calculator does it for you and also tells you the weekday, ISO week number and day of the year of the result.
How months are added
Adding months keeps the same day number when possible: March 15 plus one month is April 15. When the target month is shorter, the result moves to the last day of that month — January 31 plus one month becomes February 28 (or 29 in a leap year). This matches the convention used by most spreadsheets and banking systems. Years and months are applied first, then weeks, then days.
Calendar days vs. business days
Calendar days count every day. Business days skip Saturdays and Sundays, which is how many delivery times, payment terms and legal deadlines are measured. Public holidays are not skipped, because they differ from country to country; if a holiday falls in your range, add one more business day.
Common date periods
| Period | Typical use |
|---|---|
| 14 days | Return windows, cooling-off periods |
| 30 days | Invoice terms, free trials |
| 90 days | Probation periods, visa limits, warranty windows |
| 180 days | Six-month reviews, travel rules |
| 280 days (40 weeks) | Length of a typical pregnancy |
| 1 year | Contracts, subscriptions, anniversaries |
What is an ISO week number?
The ISO 8601 standard numbers weeks from 1 to 52 (or 53), with weeks starting on Monday. Week 1 is the week containing the year's first Thursday. Week numbers are widely used in business planning, manufacturing and school calendars, particularly in Europe.
Want to know how far apart two dates are instead? Use the days between dates calculator.
Frequently Asked Questions
What date is 90 days from today?
Leave the start date as today, choose Add and enter 90 days. The calculator shows the exact date and weekday.
What happens when I add a month to January 31?
Because February has no 31st, the result is the last day of February — the 28th, or the 29th in a leap year.
Do business days include holidays?
Only weekends are skipped. Public holidays vary by country, so add an extra day for each holiday that falls in your period.
Can I combine years, months, weeks and days?
Yes. Enter any combination; years and months are applied first, then weeks and days.
Disclaimer: Calculations use the Gregorian calendar and your device's local time zone. Results are provided as-is for informational purposes.
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