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Days Between Dates Calculator

Counting the days between two dates, or adding a number of days to a date, is a calendar arithmetic problem. Both operations reduce to converting each date to a day number, doing simple addition, and converting the result back to a calendar date.

Days between

262

Whole weeks between
37
New date: day
31
New date: month
1
New date: year
2,026
New date: weekday (0 = Sunday)
6

Values update as you type. This calculator covers the single scenario its formula assumes — see Common Mistakes for what it leaves out.

The formula this calculator uses

Days between = day number of later date - day number of earlier date

From date
The starting date
To date
The ending date
Offset
Days to add to or subtract from the from date

How to check the result by hand

  1. 1

    Convert the from date

    Apply the Julian day formula to the day, month and year of the starting date to get its day number.

  2. 2

    Convert the to date

    Apply the same formula to the ending date. The two day numbers are now comparable.

  3. 3

    Subtract for the difference

    The to day number minus the from day number is the exact number of days between the dates.

  4. 4

    Add the offset

    Add the offset in days to the from day number, then convert the result back to a calendar date.

  5. 5

    Read the weekday

    Take the day number modulo seven and offset it so that zero is Sunday. That gives the day of the week for the new date.

For worked examples, common mistakes and the limits of this formula, read the full How To Calculate Days Between Dates page.