Why "date plus 90 days" needs a calculator
Adding days across month boundaries is deceptively easy to get wrong by hand. Months have 28, 29, 30, or 31 days; leap years add a day to February every four years (with century exceptions); and "3 months from January 31" isn't even well-defined until you pick a convention. This tool does exact calendar arithmetic: day-based additions count real days one by one through the calendar, and month-based additions land on the same day-of-month, clamping to the month's last day when needed — so January 31 + 1 month = February 28 (29 in leap years), exactly how spreadsheets and payroll systems behave.
Calendar days vs. business days
Many deadlines are written in business days: "your refund will arrive in 10 business days", "respond within 5 business days". In business-days mode, every step of the count lands only on a Monday–Friday. Tick the holidays option and the calculator also passes over the eleven US federal holidays for 2025, 2026, and 2027 — using the observed dates, so when July 4 falls on a Saturday (as in 2026), Friday July 3 is treated as the holiday, just like banks and government offices do. For counting business days between two known dates, use the dedicated business days calculator.
Everyday uses
- Probation and trial periods: 30/60/90 days from a start date — the classic use, and why 90 is the default above.
- Visa and travel rules: "90 days within any 180-day period" starts with knowing your exact day-90 date.
- Returns and warranties: last day of a 30-day return window or 12-month warranty (use months for the latter).
- Medical schedules: a follow-up "in 6 weeks" — 42 real days, landing on a precise weekday you can plan around.
- Working backwards: subtract to find start dates — if a project is due June 1 and needs 45 days, when must it begin?
The result always shows the day of the week, because "June 14" matters less than "that's a Sunday" when you're planning. And if the resulting date is something you're waiting for, drop it into the countdown timer to watch it approach — or check how far away it is with the date duration calculator.
Frequently asked questions
What date is 90 days from today?
Enter today as the start date, Add, 90, days. The tool returns the exact date and weekday, leap-year aware.
What is January 31 plus one month?
February 28 (February 29 in leap years) — the standard "clamp to last day of month" convention.
How does skip-weekends mode work?
Each counted step lands only on Monday–Friday, and optionally skips US federal holidays 2025–2027 (observed dates).
Can I go backwards in time?
Yes — choose Subtract. Business-days mode works backwards too.