Date Calculator – Add or Subtract Days from a Date
Add or subtract days, weeks, months and years from a date, or find the gap between two dates.
About the Date Calculator
What is the Date Calculator?
A date calculator either adds and subtracts a span of time from a date or measures the number of days between two dates.
Why use this calculator?
Deadlines, pregnancy milestones, contract terms and event planning all involve date arithmetic that is awkward to do by hand.
How to use it
- Choose to add/subtract from a date or to find the difference.
- Enter the date(s).
- For add/subtract, set years, months, weeks and days (negative values subtract).
Formula
Months and years are calendar-aware; days and weeks are added afterward.
A negative value in any field subtracts that amount instead of adding it.
Frequently Asked Questions
How do I count 90 days from today?
Choose the add/subtract mode, leave the other fields at 0, and enter 90 in the days field.
Does subtracting a month always give the same day?
Not always. If the target month is shorter, the result rolls to the last valid day of that month.
Does it account for leap years?
Yes. The date logic follows the Gregorian calendar, including leap years and differing month lengths.
Are weekends and holidays excluded?
Only if the calculator says so. By default, results count every calendar day; use a business-day option where available.
Which time zone is used?
Calculations use whole calendar dates and are time-zone independent unless a time-of-day is involved.
Is this calculator free to use?
Yes. Every calculator on this site is completely free, with no hidden fees, no subscriptions and no limits on how many times you can use it.
How accurate are the results?
We use standard, widely accepted formulas and calculate in your browser using double-precision arithmetic. Results are rounded for readability, so treat them as reliable estimates rather than a guarantee. Real-world factors can vary the true figure.
Can I add this calculator to my own website?
Yes. Open this calculator page and use the "Add to your website" box in the sidebar to copy a ready-made iframe snippet, then paste it into any HTML page.
Does it work on a phone or tablet?
Yes. The layout is fully responsive, so it works on desktops, laptops, tablets and mobile phones, and every input adapts to touch screens.
Is the information I type kept private?
Yes. All calculations run locally in your browser. Nothing you enter is uploaded, stored or shared with anyone.