Date Calculator
Add or subtract days, weeks, months or business days from any date
Nov 12, 2026 plus 30 days.
Counting the days between two dates? The days between dates calculator does that, business days too.
How it works and common questions
Common date calculations
- 90 days from Jan 1, 2027 is Thursday, Apr 1, 2027.
- 30 days from Dec 1, 2026 is Thursday, Dec 31, 2026.
- 100 days from Jan 1, 2027 is Sunday, Apr 11, 2027.
- 30 days before Mar 1, 2027 is Saturday, Jan 30, 2027.
- Jan 31, 2027 + 1 month is Feb 28, 2027: February has no 31st.
- Jan 31, 2028 + 1 month is Feb 29, 2028, as 2028 is a leap year.
- Feb 29, 2028 + 1 year is Feb 28, 2029, and + 4 years is Feb 29, 2032.
- 6 months from Nov 30, 2026 is May 30, 2027.
- 10 business days from Mon, Nov 16, 2026 is Monday, Nov 30, 2026, or Dec 1, 2026 skipping Thanksgiving.
- 5 business days from Fri, Dec 18, 2026 is Dec 25, 2026, or Monday, Dec 28, 2026 skipping Christmas Day.
How it works
Days and weeks are counted on the calendar: day 1 is the day after the start date, and a week is 7 days. Months and years keep the day of the month, so 6 months from May 15 is November 15. When the new month is shorter, the date stops at its last day: January 31 plus a month is February 28.
Business days are Monday to Friday. With “Skip US federal holidays” ticked, the 11 federal holidays are skipped on the day they’re observed (a Saturday holiday on the Friday before, a Sunday one on the Monday after). State holidays and other countries’ holidays aren’t included.
Questions
How do I calculate a date from a number of days?
Pick the start date, choose Add or Subtract and type the days; the date appears at once. By hand, count forward month by month: 90 days from January 1, 2027 is 30 days to January 31, 28 more to February 28, 31 more to March 31 (89 in all) and one more, so Apr 1, 2027.
What date is 90 days from today?
The calculator starts on today’s date, so tap “+ 90 days” (or type 90 in Days) and it shows the date and its weekday. Ninety days is 12 weeks and 6 days, so the answer is always the weekday before today’s, about three months on.
Does adding days count the start date?
No. Day 1 is the day after the start date, so 30 days from November 1 is December 1, and 1 day from today is tomorrow. If a deadline is “within 30 days, counting today”, subtract one day from the answer.
What is one month after January 31?
February 28 (Feb 28, 2027), or February 29 in a leap year. Adding months keeps the day of the month, and when the new month is shorter it stops at its last day, as Excel’s EDATE and most date libraries do. Two months after January 31 is March 31.
How does the calculator handle leap years?
February has 29 days in years divisible by 4, except century years not divisible by 400 (2000 was a leap year, 2100 won’t be). Adding a year to February 29 gives February 28 (Feb 28, 2029), and adding days counts February 29 as a day like any other.
How do I add business days to a date?
Choose Business days, type the number and the calculator skips Saturdays and Sundays. The start day doesn’t count, so Friday plus 1 business day is Monday. Tick “Skip US federal holidays” to skip those as well, on their observed dates: 10 business days from Monday, November 16, 2026 is Nov 30, 2026, or Dec 1, 2026 skipping Thanksgiving.
In what order are years, months, weeks and days added?
Years and months first, then weeks and days, the way “1 month and 1 day from January 31” is meant: January 31 + 1 month is February 28, then + 1 day is Mar 1, 2027. Subtracting works the same way backwards.
Does daylight saving time change the answer?
No. The calculator counts whole calendar days, so the day the clocks change counts as one day even though it is 23 or 25 hours long.
Related tools
- Days between dates calculator — how many days, weeks, months and business days from one date to another
- Time duration calculator — the exact time between two dates and times
- Countdown timer — count down to the date you found, and share it
- Holidays 2026–2027 — upcoming holidays and the US federal holiday dates