How to Add Days to a Date in Excel, Plus Every Key Date Formula

To add days to a date in Excel, add the number to the date: =A1+30. If A1 holds Friday, October 2, 2026, the formula returns Sunday, November 1, 2026. To add working days instead, skipping weekends, use =WORKDAY(A1,10), which returns Friday, October 16, 2026.

Excel’s date functions are simple once you know that a date is just a number. This guide covers plain date arithmetic and the six functions that handle almost every date job: DATE, EDATE, EOMONTH, WORKDAY, NETWORKDAYS and DATEDIF. Every example below was checked against the same engine that runs our date calculator, so you can use the calculator to confirm your spreadsheet.

How Excel stores dates

Excel stores each date as a serial number: January 1, 1900 is 1, January 2, 1900 is 2, and so on. That’s why adding 30 to a date moves it 30 days, and why subtracting one date from another gives the days between them.

Two practical consequences:

• If a result shows a five-digit number instead of a date, the formula is right; the cell just needs a date format.
• Microsoft recommends entering dates with the DATE function, such as DATE(2026,10,2), rather than typing them as text, because text dates can be misread. Its WORKDAY documentation makes the same point.

Add days to a date in Excel

• =A1+30 adds 30 calendar days. From October 2, 2026: Sunday, November 1, 2026.
• =A1-30 subtracts them: Wednesday, September 2, 2026.
• =A1+90 gives Thursday, December 31, 2026, a common “90 days from today” deadline.
• =TODAY()+30 always counts from the current date, so the result changes each day.

To add weeks, multiply: =A1+7*6 adds six weeks. Ready-made answers are on pages like 30 days from today.

DATE: build or adjust a date

=DATE(year,month,day) turns three numbers into a date. It also rolls over cleanly, which makes it useful for date math:

• A month above 12 carries into the next year: =DATE(2026,14,1) returns Monday, February 1, 2027.
• A day beyond the end of the month carries into the next month, and a zero or negative day counts back. Microsoft’s example: =DATE(2008,1,-15) returns December 16, 2007.
• =DATE(YEAR(A1),MONTH(A1),DAY(A1)+90) adds 90 days, the same as =A1+90.

Use four-digit years. Microsoft notes that a year from 0 to 1899 is added to 1900, so DATE(26,10,2) means October 2, 1926, not 2026.

EDATE and EOMONTH: months and month ends

Months have different lengths, so “add one month” can’t be done by adding days. =EDATE(A1,n) moves a date by whole months and keeps the day of the month: =EDATE(A1,3) on October 2, 2026 returns Saturday, January 2, 2027, and =EDATE(A1,12) returns Saturday, October 2, 2027. Use a negative number to go back.

Month-end dates need care. Our date calculator clamps a missing day to the last day of the month, so January 31, 2027 plus one month is February 28, 2027. If you work with month ends often, test a few in your own spreadsheet, or use EOMONTH, which is built for them.

=EOMONTH(A1,0) returns the last day of the current month (October 31, 2026 for October 2), and =EOMONTH(A1,1) the last day of next month. =EOMONTH(A1,-1)+1 gives the first day of the current month. Both functions return serial numbers, so format the cells as dates.

WORKDAY: add business days

=WORKDAY(start_date,days,[holidays]) steps forward (or back, with a negative number) by working days, skipping Saturdays and Sundays. The start date itself isn’t counted, so 10 working days from a Friday lands on the Friday two weeks later. Our engine reproduces Microsoft’s own example: 151 workdays from October 1, 2008 is April 30, 2009, or May 5, 2009 with its three sample holidays.

The holidays argument takes a range of dates. For the US federal list, copy the dates from the 2027 holiday calendar into a column and point the formula at it. If your weekend isn’t Saturday and Sunday, Microsoft’s WORKDAY.INTL lets you choose the weekend days. Our business days calculator works like WORKDAY and shows the result with and without US federal holidays.

NETWORKDAYS: count business days

=NETWORKDAYS(start_date,end_date,[holidays]) counts the working days between two dates, and it counts both the start and the end date. Microsoft’s own example counts 110 workdays from October 1, 2012 to March 1, 2013.

• =NETWORKDAYS(DATE(2026,10,1),DATE(2026,10,31)) returns 22, the weekdays in October 2026.
• With Columbus Day, October 12, in the holiday list, it returns 21.

Because NETWORKDAYS includes both ends, it can be one higher than a calculator that counts from the day after the start date. Our guide on how to count days between dates explains the difference.

DATEDIF: years, months and days

=DATEDIF(start_date,end_date,unit) returns the gap in the unit you choose. Microsoft keeps it to support older workbooks from Lotus 1-2-3, and it still works in current versions. With A1 as July 20, 1990 and B1 as October 2, 2026:

• "Y" returns 36, the complete years.
• "YM" returns 2, the months left over after the years.
• "MD" returns 12, the days left over after the months.
• "D" returns 13,223, the total days, the same as =B1-A1.

So the age is 36 years, 2 months and 12 days, which matches our age calculator. Microsoft warns on its DATEDIF page that the “MD” unit can give a negative, zero or inaccurate result in some cases, so double-check it near month ends.

Frequently asked questions

How do I add days to a date in Excel?

Add the number directly: =A1+30. Format the result cell as a date if it shows a serial number. For business days, use =WORKDAY(A1,30).

How do I add months to a date in Excel?

Use EDATE: =EDATE(A1,3) adds three months and keeps the day of the month. October 2, 2026 plus three months is January 2, 2027.

How do I add business days excluding holidays?

Put the holiday dates in a range and pass it as the third argument: =WORKDAY(A1,10,H1:H12). Weekends are skipped automatically.

Why does my date formula show a number?

Excel stores dates as serial numbers, with January 1, 1900 as 1. The formula is working; change the cell’s format to a date.

Does NETWORKDAYS include the start date?

Yes. NETWORKDAYS counts both the start date and the end date if they are working days.