Add or Subtract Days Calculator

Add or subtract time from a date

The Add or Subtract Days Calculator takes a starting date and adds or subtracts a number of days, weeks, months, or years to give you the resulting date — including the day of the week. It removes the hassle of counting on a calendar and correctly handles month lengths and leap years.

What you can work out

• Deadlines — "30 days from today" for a payment or return window.
• Due dates — adding weeks to a start date.
• Anniversaries and reminders — a year or several months ahead.
• Backdating — subtracting time to find a past date.

How to use it

1. Choose your start date.
2. Select Add or Subtract.
3. Enter the amount and pick days, weeks, months, or years.
4. Read the resulting date and its weekday instantly.

Days vs months vs years

Unit	How it is applied
Days / Weeks	Exact day counting (weeks = 7 days)
Months	Calendar months, adjusting for month length
Years	Calendar years, accounting for leap days

Why month math is tricky

Adding "one month" is not the same as adding 30 days, because months vary from 28 to 31 days. This calculator uses true calendar arithmetic: add a month to January 15 and you get February 15. Edge cases near month ends are handled the way calendars do, so results stay intuitive and correct.

Common scenarios

Need to know the date 90 days from now for a contract? Want the date six weeks before an event to send invitations? Curious what day of the week your deadline falls on? This tool answers all of those in one step, with the weekday shown so you can plan around weekends and holidays.

Private and free

All calculations run in your browser, with nothing uploaded and no limits. Use it as often as you like, free.