Add Days to Date Calculator

Add days to date calculator online — add or subtract days, weeks, months or years from any date. Use the free Add Days to Date Calculator below — enter your values and get instant results, right in your browser. Logic: days and weeks are added as exact 24-hour multiples from UTC midnight; months and years use calendar arithmetic (e.g. adding 1 month to 31 January lands on the last day of February). The weekday is derived from the resulting date.

How to use the Add Days to Date Calculator

Contracts say "delivery in 45 days", visas allow "90 days from entry", and warranties run "2 years from purchase" — but what actual date is that? Mental calendar math across month boundaries is unreliable. This add days to date calculator online does it perfectly: pick a start date, add or subtract any number of days, weeks, months or years, and get the exact resulting date plus its weekday, instantly.

  1. Open the Add/Subtract tab of the calculator.
  2. Enter your starting date in the date field.
  3. Choose + or −, then type the number and pick days, weeks, months or years.
  4. Click Calculate to see the resulting date.
  5. Note the weekday shown — handy for checking if a deadline falls on a weekend.

Formula

Logic: days and weeks are added as exact 24-hour multiples from UTC midnight; months and years use calendar arithmetic (e.g. adding 1 month to 31 January lands on the last day of February). The weekday is derived from the resulting date.

Worked example

Start date 12 October 2026, operator +, 45 days. Click Calculate. Result: 26 November 2026, a Thursday. So a "45-day delivery" promise made today means 26 November — now you know exactly. The weekday display also shows it is a Thursday, so weekend deadlines never catch you by surprise.

Frequently asked questions

It lands on the last valid day of the target month — 28 or 29 February — following standard calendar rules.

Yes. Choose the minus operator to go backwards, e.g. 90 days before a deadline.

No, it counts calendar days. Use the Business Days Counter if you need working days only.

Business Days Counter Business days between two dates calculator — count working days excluding weekends for deadlines. Birthday Countdown How many days until my birthday — live countdown to your next birthday with days, hours and seconds. Wedding Countdown Timer Wedding countdown timer online — tick down to the big day with days, hours, minutes and seconds.