DATE CALCULATOR

Contracts, returns windows, notice periods and warranties are usually written in calendar days — weekends and holidays included. A 30-day return window that starts on a Friday ends on a Sunday, and plenty of people lose the window assuming they had until Monday. When a document doesn't explicitly say "business days," assume calendar days and give yourself a buffer.

What is one month after January 31? There is no February 31, so software has to make a choice. The standard convention — used here and in most spreadsheets — is to clamp to the last valid day of the target month, giving February 28 (or 29 in a leap year). It's a reasonable rule, but it means adding a month and then subtracting one doesn't always bring you back where you started. When precision matters legally, count in days.

Most U.S. legal and administrative deadlines exclude the triggering day and start the count from the next day — "within 14 days of receipt" usually means the day after receipt is day one. This calculator counts pure calendar arithmetic from the date you enter, so if a rule says "the day after," advance your start date by one before calculating.

Once you have the date, don't leave it in a browser tab. Our free reminder tool drops it straight into your own calendar as a Google Calendar event or an iCal file — created entirely in your browser, with nothing stored on our servers.

The reason "what date is 90 days from today" is such a common search is that a handful of very ordinary situations run on fixed day counts. A 30-day notice to end a tenancy. A 90-day probationary period at a new job. A 60-day window to elect continuing health coverage after leaving a job. Return policies at 14, 30 or 90 days. Warranty claims, visa validity, and the 30-day deadline to register a vehicle in a new state. Borrowing runs on the same arithmetic: mortgage rate locks are sold in 30, 45 or 60 day terms, and if the closing drifts past the lock date an extension usually costs money — our mortgage payment calculator shows what the rate itself is worth per month. Insurance works to fixed windows as well, with renewal and non-renewal notices typically owed 30 to 45 days ahead, which is the window you have to shop the policy; our insurance cost calculator gives you a figure to compare against. In nearly all of these the count is in calendar days from a triggering event, which is exactly what the tool above computes — but read the document, because the triggering event is where people go wrong far more often than the arithmetic.

One of the most common uses of a date calculator has nothing to do with contracts. The standard estimate of a due date, known as Naegele's rule, adds 280 days — exactly 40 weeks — to the first day of the last menstrual period. Nine calendar months is not the same thing: depending on where in the year you start, nine months can be anywhere from 273 to 276 days, which is why "nine months" and the clinic's date rarely match. Set the tool to add 280 days and you get the same figure a midwife would. It is an estimate either way; only about one birth in twenty actually arrives on it.

Planning usually runs in reverse. You know the wedding, the closing, the trip or the filing deadline, and what you need is when everything before it has to happen. Enter the fixed date and subtract instead of adding: 90 days back for invitations, 45 for a final headcount, 14 for the rehearsal. Working backwards also exposes collisions early — if two milestones land in the same week, you find out now rather than in the week itself. Once each date is settled, our countdown timer tracks the one that matters most.

A frequent worry is whether the spring-forward and fall-back transitions throw date arithmetic off by a day. They don't. Adding 30 days to a date is calendar arithmetic, not clock arithmetic — the answer is the same regardless of any hour that was skipped or repeated in between. This matters in software, where naively adding "30 × 24 hours" to a timestamp can land on the wrong calendar day across a transition. This calculator works on calendar dates in your own local time zone, so that class of off-by-one error can't occur. Where the clock genuinely matters is across time zones, and our time zone converter handles that side.

Three different counts hide behind the word "days." Calendar days include everything and are the default in most consumer contracts. Business days exclude weekends and usually federal holidays, and appear in shipping estimates, bank transfers and court rules. Working days can mean either, depending on the employer. If a document says only "days," it almost always means calendar days. When it says business days, switch to our business day calculator, which skips weekends and U.S. federal holidays, and use days between dates when you need both counts side by side.