📆 Add or Subtract Days From a Date
Find out what date it will be (or was) after adding or subtracting days, weeks, months, or years.
Need to know what date is 90 days from today, when a 30-day trial expires, or what date falls 6 weeks before your project kicks off? The Add or Subtract Days calculator answers exactly that. Choose a start date, pick how much time to move forward or backward, and instantly get the resulting calendar date — plus its weekday.
This is one of the most common date questions people ask: counting forward for deadlines, renewals, and delivery estimates, or backward to reconstruct a timeline from a known milestone. Everything runs locally in your browser, so your dates never leave your device.
For example, 90 days after January 1, 2026 is April 1, 2026. 180 days before November 30, 2026 is June 3, 2026. Try it with any date and offset you need.
How Does the Calculation Work?
The tool starts from your chosen date, normalized to midnight UTC to stay consistent across time zones. It then applies your offset in the selected unit. For days and weeks it works directly on the millisecond timestamp (adding 86,400,000 ms per day, with leap-year dates handled automatically by the JavaScript Date engine).
For months and years it adds to the calendar components first, so adding 1 month to January 31 correctly rolls over to the last day of the following month rather than skipping to an invalid date. This matches how real calendars behave — adding a month to January 31, 2026 gives February 28, 2026 (or February 29 in a leap year).
Practical Examples
90 days from today: If today is September 21, 2026, adding 90 days lands on December 20, 2026. Perfect for trial periods, visa windows, and 90-day marketing plans.
Six weeks from a date: Adding 6 weeks to a starting date gives you 42 days later — useful for training blocks, interim reviews, and short project sprints.
Months and years: Adding 18 months to May 15, 2026 gives November 15, 2027. Adding 5 years to February 29, 2024 (a leap day) yields February 28, 2029, since 2029 is not a leap year — the calendar adjusts gracefully.
What If the Date Is in the Future or Past?
This tool is bidirectional. Use Add to plan forward — deadlines, expirations, due dates. Use Subtract to reconstruct past events or work backward from a known end date, such as counting 30 days back from a delivery milestone. The weekday of the resulting date is always shown, so you can instantly see, for example, whether your 90-day deadline falls on a weekend.
Try also:
Frequently Asked Questions
What date is 90 days from today?
Select today as the start date, choose Add with an amount of 90 days, and the tool instantly shows the exact calendar date — December 20, 2026 if today is September 21, 2026. You can do this for any number of days.
Can I subtract days instead of adding?
Yes. Switch the operation to Subtract and enter any amount. Counting backward is just as accurate and useful for reconstructing timelines, calculating warranty windows, or finding dates prior to a known milestone.
Does it support weeks, months, and years too?
Absolutely. Choose the unit next to the amount — days, weeks, months, or years. Adding 1 month to January 31 correctly returns the last day of the next month rather than an invalid date, and leap years are handled automatically.
Why does adding one month to January 31 give February 28?
Because February has fewer than 31 days. Instead of producing an invalid date like February 31, the calculator rolls over to the last valid day of that month (February 28, or February 29 in a leap year). This matches how real-world calendar math works.
Is this calculator free and private?
Yes. Everything runs locally in your browser with JavaScript — no data is sent to any server. Use it as often as you like, completely free, with no account or sign-up.