How are dates a certain number of days before or after calculated?

The reference date counts as day 0, and the result moves forward with plus or backward with minus by the number of days you enter, shown with its day of the week. Leap years are handled automatically, so month-end and year-crossing calculations stay accurate.

What is the maximum number of days I can enter?

You can enter any whole number from 0 up to about 100 years (36,500 days). The entered days are also converted into weeks and days so you can grasp the rough length of the period.

How is this different from counting days between two dates?

This tool adds or subtracts days from a reference date to find a resulting date. If you already know two dates and want the number of days between them, use the days-between tool instead.

Date Plus Days Calculator

Add or subtract days from a base date to find the date a given number of days before or after, complete with the day of the week. Includes a weeks breakdown, great for deadlines, anniversaries, and expiry dates.

Last updated: June 25, 2026

Input

Base date

YYYY/MM/DD

Number of days

days

Result

Enter a base date and a number of days.

How it works

Pick a base date, enter the number of days you want to add (or subtract), and choose "After (+)" or "Before (−)" to see the resulting date along with its day of the week.
"After (+)" finds a date in the future relative to the base date, and "Before (−)" finds a date in the past. The base date counts as day 0, and the result is shifted forward or backward by the number of days you enter.
The number of days you enter is also broken down into weeks and days so you can quickly gauge the overall length of the period.
Enter the number of days as a whole number of 0 or more, up to about 100 years (36,500 days). Leap years are taken into account automatically.
Use it to check future or past dates such as deadlines, submission dates, contract expiry dates, anniversaries, and the number of days until an event.

Frequently asked questions

How are dates a certain number of days before or after calculated?: The reference date counts as day 0, and the result moves forward with plus or backward with minus by the number of days you enter, shown with its day of the week. Leap years are handled automatically, so month-end and year-crossing calculations stay accurate.
What is the maximum number of days I can enter?: You can enter any whole number from 0 up to about 100 years (36,500 days). The entered days are also converted into weeks and days so you can grasp the rough length of the period.
How is this different from counting days between two dates?: This tool adds or subtracts days from a reference date to find a resulting date. If you already know two dates and want the number of days between them, use the days-between tool instead.

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