Add Days to a Date
Add or subtract days, weeks, months, years or business days from any date
September 25, 2026 + 30 days = Sunday, October 25, 2026. Pick a start date, choose add or subtract, and enter an amount in days, weeks, months, years or business days to get the exact result date and its weekday.
Add days to a date
LiveHow to add days to a date
Adding days is exact counting on the calendar: the start date is day 0, the next day is day 1, and the count rolls straight over month and year ends. September has 30 days, so September 25 plus 5 days is September 30, and plus 30 days is October 25. Weeks are simply 7 days each. To measure the gap between two dates you already know, the days between dates calculator runs the same arithmetic backward, and the rest of the date calculators cover ages, week numbers and Unix time.
- Choose the start date. It defaults to today.
- Select Add or Subtract, then type a whole number. Decimals are rounded to the nearest whole number.
- Pick the unit: days, weeks, months, years or business days.
- Read the result date with its weekday. The line below it shows how many calendar days separate the two dates.
How each unit is counted
- Days and weeks move by an exact number of calendar days.
- Months keep the same day of the month. If the target month is too short, the result becomes its last day, so January 31, 2026 plus 1 month is February 28, 2026.
- Years are counted as 12 months, so February 29, 2028 plus 1 year is February 28, 2029.
- Business days step forward (or back) one day at a time from the day after the start date and count only Monday to Friday. Public holidays are not excluded.
How do I add days to a date in Excel or Google Sheets?
Type =A2+30 to add 30 days to the date in A2; use =EDATE(A2,1) to add one calendar month and =WORKDAY(A2,10) to add 10 business days.
Spreadsheets store dates as serial day numbers, so plain addition moves a date by whole days, exactly as the calculator above does. With September 25, 2026 in A2, =A2+30 returns October 25, 2026 and =A2-30 returns August 26, 2026. If you see a number such as 46320 instead of a date, format the cell as a date.
- EDATE keeps the day of the month and clamps to the month's end, so
=EDATE(DATE(2026,1,31),1)gives February 28, 2026, the same rule this calculator uses. - WORKDAY skips Saturdays and Sundays and starts counting the day after the start date, matching the Business days option:
=WORKDAY(A2,10)gives October 9, 2026. - Holidays can be excluded by adding a range, as in
=WORKDAY(A2,10,H2:H12), something this calculator does not do. - Other weekends, such as Friday and Saturday, need
WORKDAY.INTL, which takes a weekend code.
Is 6 months the same as 180 days?
No: 6 months from September 25, 2026 is March 25, 2027, which is 181 days later, while 180 days lands on March 24, 2027. Month lengths vary, so month and day counts rarely match exactly.
| Added | Result from September 25, 2026 | Calendar days |
|---|---|---|
| 1 month | Sunday, October 25, 2026 | 30 |
| 3 months | Friday, December 25, 2026 | 91 |
| 6 months | Thursday, March 25, 2027 | 181 |
| 12 months | Saturday, September 25, 2027 | 365 |
| 18 months | Saturday, March 25, 2028 | 547 |
| 24 months | Monday, September 25, 2028 | 731 |
Which months a period crosses decides its length. With this calculator's month-end rule, any 6-month span runs 181 to 184 days, depending on whether it includes February and how many 31-day months it spans. A 12-month span is 365 days, or 366 when it crosses February 29, as it does from September 25, 2027 to September 25, 2028.
So when a lease, warranty or probation period says 6 months, use the Months unit; when it says 180 days, use Days. The two answers differ by a day or more, and a contract usually means exactly what it says.
Adding days to September 25, 2026
Common offsets from a Friday start date, checked against Python's datetime library. Negative rows subtract days.
| Offset | Result date | Weekday |
|---|---|---|
| +7 days (1 week) | October 2, 2026 | Friday |
| +14 days (2 weeks) | October 9, 2026 | Friday |
| +30 days | October 25, 2026 | Sunday |
| +45 days | November 9, 2026 | Monday |
| +60 days | November 24, 2026 | Tuesday |
| +90 days | December 24, 2026 | Thursday |
| +100 days | January 3, 2027 | Sunday |
| +180 days | March 24, 2027 | Wednesday |
| +365 days | September 25, 2027 | Saturday |
| +1,000 days | June 21, 2029 | Thursday |
| −30 days | August 26, 2026 | Wednesday |
| −90 days | June 27, 2026 | Saturday |
Month-end and leap-year rules
Adding months is not the same as adding 30 days. This is how the calculator resolves dates that do not exist in the target month.
| Calculation | Result | Why |
|---|---|---|
| January 31, 2026 + 1 month | February 28, 2026 | February 2026 has only 28 days |
| January 31, 2028 + 1 month | February 29, 2028 | 2028 is a leap year |
| January 31, 2026 + 2 months | March 31, 2026 | March has a 31st |
| February 28, 2026 + 1 month | March 28, 2026 | The day number stays 28 |
| March 31, 2026 − 1 month | February 28, 2026 | Moved to the last day of February |
| August 31, 2026 + 6 months | February 28, 2027 | 2027 is not a leap year |
| October 31, 2026 + 1 month | November 30, 2026 | November has 30 days |
| February 29, 2028 + 1 year | February 28, 2029 | No February 29 in 2029 |
| February 29, 2028 + 4 years | February 29, 2032 | 2032 is a leap year |
Inclusive or exclusive: is the start date day 1?
This calculator treats the start date as day 0, which is how most date libraries and most legal counting rules work. If your contract or policy counts the start date as day 1, the last day of a 30-day period comes one day sooner: for a start of September 25, 2026, that is October 24 rather than October 25. To get that answer here, add one day fewer than the stated period.
US federal courts follow a similar exclusive rule. Under Rule 6(a) of the Federal Rules of Civil Procedure, you exclude the day of the event that triggers the period, count every day including weekends and holidays, and if the last day falls on a weekend or legal holiday, the period runs until the next day that is not. State courts and other countries have their own rules, so check the one that applies.
Why chaining months can drift
Because each month step clamps to the end of a short month, adding one month twice is not always the same as adding two months at once. January 31, 2026 plus 1 month is February 28; plus another month is March 28. January 31 plus 2 months in a single step is March 31. For recurring monthly dates, always count from the original start date.
How do you add business days to a date?
Count forward one weekday at a time, starting the day after the start date, and skip every Saturday and Sunday. Starting from Friday, September 25, 2026, the calculator gives:
- +5 business days: Friday, October 2, 2026 (7 calendar days).
- +10 business days: Friday, October 9, 2026 (14 calendar days).
- +20 business days: Friday, October 23, 2026 (28 calendar days).
- −3 business days: Tuesday, September 22, 2026.
Counting always starts with the day after the start date, so from Saturday, September 26, one business day later is Monday, September 28. Public holidays are counted as working days. If your office closes on Columbus Day (Monday, October 12, 2026) or Thanksgiving (Thursday, November 26, 2026), add one business day for each closure that falls inside your period.
When you need to add days to a date
- HR and employment: two-week notice periods, 90-day probation reviews, benefit enrollment windows and return dates from leave, such as the 12 workweeks of the US Family and Medical Leave Act.
- Invoices and contracts: net-30 or net-60 payment terms, cancellation windows, warranty expiry and renewal notice deadlines.
- Travel and visas: the last day of a permitted stay or the date a passport must remain valid until.
- Health: an estimated due date is commonly calculated as 280 days (40 weeks) after the first day of the last menstrual period; January 1, 2026 plus 280 days is October 8, 2026. Your healthcare provider will confirm the actual date.
- Personal planning: 100-day countdowns, habit streaks and the date someone reaches a milestone, which the age calculator also shows.
If a deadline is set in another city's time, check the hour too with the EST to PST converter, and for durations in hours or minutes use the time converter.
Sources and further reading
The standards and references behind the numbers on this page. Links open in a new tab.
Standards and official sources
Further reading
- Gregorian calendarWikipedia
Add days to date FAQs
Short, exact answers to what people ask most.
What date is 30 days from September 25, 2026?
30 days after Friday, September 25, 2026 is Sunday, October 25, 2026. The start date itself is not counted.
What date is 90 days from September 25, 2026?
90 days after September 25, 2026 is Thursday, December 24, 2026. For 90 days from any other date, set that date as the start and enter 90.
What is January 31 plus one month?
This calculator returns the last day of February: February 28 in a common year such as 2026, or February 29 in a leap year such as 2028. Other tools may roll over to early March instead.
Does the business days option skip public holidays?
No. It skips Saturdays and Sundays only, because holidays differ by country, state and employer. Add one business day for each holiday that falls within your period.
Is the start date counted when adding days?
No. The start date is day 0, so adding 1 day gives the next calendar day. If your rule counts the start date as day 1, enter one day fewer.
How do I subtract days from a date?
Choose Subtract in the Add or subtract menu, then enter the number of days, weeks, months, years or business days. For example, September 25, 2026 minus 30 days is August 26, 2026.
What date is 60 days from September 25, 2026?
60 days after Friday, September 25, 2026 is Tuesday, November 24, 2026. It falls two days before Thanksgiving, which is on November 26, 2026.
What date is 120 days from September 25, 2026?
120 days after September 25, 2026 is Saturday, January 23, 2027, in the next calendar year. The calculator rolls over year ends automatically.
How many weeks is 90 days?
90 days is 12 weeks and 6 days, or about 12.86 weeks. To land on the same weekday as the start date, add 91 days, which is exactly 13 weeks.
Related conversions
Dates follow the Gregorian calendar and ISO 8601; every example was checked with Python's datetime library, spreadsheet functions follow Microsoft Excel and Google Sheets documentation, and court counting rules are from Rule 6(a) of the Federal Rules of Civil Procedure. Last updated . How we verify our numbers.