How to use the date column difference calculator
- Paste a table with a header row. Name the start date column and the end date column, or give their numbers.
- Choose the date layout your table uses: year-month-day, month/day/year or day/month/year.
- Choose the unit: days, weeks, whole months, whole years or business days. For business days you can list holidays to skip.
- Read the summary and the first 100 rows, then download the CSV to get every row with the new column.
Formula
days = end day number - start day number (negative when the end is first)
weeks = days / 7
whole months = complete calendar months stepped from the earlier date, with the last day of a short month used when the day does not exist
business days = weekdays after the start date up to and including the end date, minus listed holidays
Dates are plain calendar dates with no time zone. Each date is checked against the calendar, so February 30 is rejected as unreadable.
Five support tickets
The sample table opens and closes five tickets. The differences in days are 4, 39, 0, -5 and 92. The fourth ticket closed before it opened, so its difference is negative, and the page counts it under rows with the end before the start.
The sum is 130 days and the average is 26 days. In whole months the same tickets give 0, 1, 0, 0 and 3. The last one runs from March 30 to June 30, which is exactly 3 months. In business days, Monday January 5 to Friday January 9 is 4, because the start day is not counted.
How months and business days are defined
Months have different lengths, so a month difference needs a rule. This page counts whole months by stepping forward from the earlier date. January 31 plus 1 month is the last day of February, so January 31 to February 28 is 1 whole month and January 31 to March 1 is 1 month and 1 day, which this page reports as 1.
Business days here are Monday to Friday, with holidays you list removed. Two dates on the same day give 0, and a weekend date at the end counts only the weekdays before it. Public holidays differ by place and year, so enter your own.
Unreadable rows
A row with a blank or unreadable date keeps its place in the result with an empty difference, and is left out of the summary. The headline note says how many rows had two readable dates and names the first few rows that did not. A wrong layout choice is the usual cause: 03/04/2026 is March 4 in month first layouts and April 3 in day first layouts.
For one pair of dates use Days Between Dates. To settle which layout a column uses before you subtract, try the Ambiguous Date Column Resolver.
Assumptions and limits
- Dates are read in the layout you choose, with four digit years from 1000.
- The first row is the header. Tables are limited to 20,000 data rows.
- Business days exclude Saturday and Sunday and the holidays you list. Other weekend patterns are not modeled.
- Weeks are shown with two decimal places, rounded half up.
- Your table stays in this browser.
Frequently asked questions
Why is a difference negative?
The end date is before the start date in that row. The page keeps the sign so you can spot data entry mistakes, and it counts those rows in the summary.
Are the start and end days both counted?
In days, the difference is the number of days between the dates, so the same day gives 0. In business days the start day is not counted and the end day is, so a Monday to the next Monday gives 5.
How do I skip public holidays?
Choose business days and list the dates as year-month-day, one per line or separated by commas. They are removed from the count whenever they fall on a weekday inside the range.
Why did some rows come out blank?
Their dates could not be read in the layout you chose. Check the separators and the order of day and month, and look for words instead of dates in the date columns.