Last updated: October 2026
Short answer: To add days to a date, count forward that many calendar days, rolling into the next month when you pass its last day. To subtract days, count backward the same way. For example, 90 days after Monday, November 2, 2026 is Sunday, January 31, 2027. In Excel or Google Sheets, use =A1+90.
This guide is about moving a date forward or back. If you already have two dates and want the gap between them, use the date difference calculator. It counts the days between two dates, with options for the end date and business days.
Common offsets from one date
The table starts from Monday, November 2, 2026 and shows the result with its weekday. Every row was computed in Python using the Gregorian calendar.
| Change | Date after (+) | Date before (−) |
|---|---|---|
| 7 days | Mon, Nov 9, 2026 | Mon, Oct 26, 2026 |
| 30 days | Wed, Dec 2, 2026 | Sat, Oct 3, 2026 |
| 45 days | Thu, Dec 17, 2026 | Fri, Sep 18, 2026 |
| 60 days | Fri, Jan 1, 2027 | Thu, Sep 3, 2026 |
| 90 days | Sun, Jan 31, 2027 | Tue, Aug 4, 2026 |
| 120 days | Tue, Mar 2, 2027 | Sun, Jul 5, 2026 |
| 180 days | Sat, May 1, 2027 | Wed, May 6, 2026 |
| 6 months | Sun, May 2, 2027 | Sat, May 2, 2026 |
| 1 year | Tue, Nov 2, 2027 | Sun, Nov 2, 2025 |
Notice that 180 days and 6 months land on different dates. Six calendar months from November 2 is May 2, but 180 days is one day short because November through April adds up to 181 days. To check the weekday of any result, use the day of the week calculator.
How to add days to a date by hand
- Find the days left in the start month. November has 30 days, so from November 2 there are 28 days left.
- Subtract them from the number you are adding. 90 − 28 = 62 days still to go, starting from the first of December.
- Take off whole months. December has 31 days, so 62 − 31 = 31 days left.
- Land in the last month. 31 days into January is January 31, 2027.
Subtracting works the same way in reverse. Count back to the end of the previous month, then step back through whole months. For 30 days before November 2: two days take you to October 31, and 28 more days take you to October 3.
Month lengths are fixed except for February:
| Days | Months |
|---|---|
| 31 | January, March, May, July, August, October, December |
| 30 | April, June, September, November |
| 28 or 29 | February (29 in a leap year) |
Calendar rules that change the answer
Days vs months: the month-end rule
Adding days is exact. Adding months is not, because months have different lengths. Spreadsheets and most date libraries handle a missing day by using the last day of the shorter month:
| Start | Add | Result |
|---|---|---|
| Jan 31, 2027 | 1 month | Sun, Feb 28, 2027 |
| Jan 31, 2028 | 1 month | Tue, Feb 29, 2028 (leap year) |
| Aug 31, 2026 | 6 months | Sun, Feb 28, 2027 |
| Feb 29, 2028 | 1 year | Wed, Feb 28, 2029 |
| Jan 31, 2027 | 30 days | Tue, Mar 2, 2027 |
| Jan 31, 2028 | 30 days | Wed, Mar 1, 2028 |
If a contract, lease or bill says “one month,” ask how the other party handles the 29th, 30th and 31st. If it says “30 days,” count days.
Leap years
A year is a leap year if it is divisible by 4, except century years, which must be divisible by 400. 2028 is a leap year, so February 2028 has 29 days. 2026 and 2027 are not, and neither is 2100. Any count of days that crosses February 29, 2028 comes out one day earlier than the same count across a normal February.
Inclusive vs exclusive counting
The normal method, used in the table above and by spreadsheets, does not count the start date. Day 1 is the day after you start. So 30 days after November 2 is December 2.
Some rules count the start date as day 1, such as a 10-day course that starts on Monday, or a hotel or leave request where both ends count. In that case, the last day is one day earlier: day 30 of a period that starts November 2 is December 1. Your contract or policy decides which method applies. When the deadline matters, check the wording before relying on either answer.
Excel and Google Sheets formulas
Both programs store dates as serial numbers, one per day, so adding a number adds days. The function names and arguments below are the same in both. They come from Microsoft’s add or subtract dates, EDATE and WORKDAY help pages, and Google’s EDATE and WORKDAY help pages (all checked October 29, 2026).
| Goal | Formula (start date in A1) | Result for Nov 2, 2026 |
|---|---|---|
| Add 90 days | =A1+90 |
Jan 31, 2027 |
| Subtract 30 days | =A1-30 |
Oct 3, 2026 |
| Add 6 months | =EDATE(A1,6) |
May 2, 2027 |
| Subtract 3 months | =EDATE(A1,-3) |
Aug 2, 2026 |
| Add 1 year | =EDATE(A1,12) |
Nov 2, 2027 |
| Add 10 business days | =WORKDAY(A1,10) |
Nov 16, 2026 |
| Add 10 business days, skipping holidays in H1:H3 | =WORKDAY(A1,10,H1:H3) |
Nov 17, 2026 |
| Days from today | =TODAY()+90 |
Updates daily |
If the result shows as a number such as 46418, format the cell as a date. EDATE returns a serial number, which is why this happens.
Adding business days
Business days usually mean Monday to Friday. To add them, skip each Saturday and Sunday as you count, and skip any holidays the rule names. Counting forward from Monday, November 2, 2026:
| Business days added | Weekends only skipped | Also skipping Nov 11, Nov 26 and Dec 25, 2026 |
|---|---|---|
| 10 | Mon, Nov 16, 2026 | Tue, Nov 17, 2026 |
| 20 | Mon, Nov 30, 2026 | Wed, Dec 2, 2026 |
| 30 | Mon, Dec 14, 2026 | Wed, Dec 16, 2026 |
The holidays in the last column are Veterans Day, Thanksgiving and Christmas Day from the OPM federal holiday list (checked October 29, 2026). Your employer, court or bank may observe a different list, so use theirs.
To count the business days between two dates you already have, tick the business-days option in the date difference calculator.
Related time and date tools
- Days, weeks and months between two dates: date difference calculator
- Exact age from a birth date: age calculator
- Hours and minutes between two clock times: time duration calculator
- Hours worked across shifts: hours calculator
Frequently asked questions
What date is 90 days from today?
Add 90 calendar days to today’s date, not counting today. If today is Thursday, October 29, 2026, then 90 days from today is Wednesday, January 27, 2027. In a spreadsheet, =TODAY()+90 gives the answer for whatever day you open it.
How do I subtract days from a date?
Count backward through the calendar, stepping into the previous month when you pass the 1st. In Excel or Google Sheets, use =A1-30. For example, 90 days before November 2, 2026 is Tuesday, August 4, 2026.
Is adding 1 month the same as adding 30 days?
No. One month keeps the same day number, while 30 days can land on a different one. From January 31, 2027, one month is February 28, 2027, but 30 days is March 2, 2027.
Does “within 30 days” include the first day?
Usually not. Standard date math starts counting the day after the start date. Some contracts and policies count the start date as day 1, which makes the deadline one day earlier. The document’s own wording decides.
How do I add business days only?
Skip Saturdays, Sundays and any listed holidays as you count. In Excel or Google Sheets, use =WORKDAY(A1, days, holidays). Ten business days after Monday, November 2, 2026 is Monday, November 16, or Tuesday, November 17 if you skip Veterans Day.
How do I find the number of days between two dates?
Subtract the earlier date from the later one, or enter both dates in the date calculator between two dates. It shows the total in days, weeks, months and years, and can include the end date or count business days only.
Bottom line: Add or subtract days for exact deadlines, and add months when the same day number matters. Watch month ends, February 29, 2028 and whether the start date counts. When you have both dates and need the gap, use the date difference calculator.