Dates and time
Date Calculator
Count the days between two dates, with business days, weeks, and months, or add and subtract days, weeks, months, and years from a date.
Maintained by Austin Witherow · Updated
Formula
Days between = End date − Start date (+ 1 if the end date counts)Weeks = Days ÷ 7, rounded down; days left = the remainderBusiness days = Days − weekend days − weekday federal holidaysNew date = Start date + months (same day of the month, clamped) + 7 × weeks + days
Key caveat
The start date counts and the end date does not, unless you turn on Count the end date too.
What this calculator is for
Count the days between two dates, or find the date a number of days, weeks, months, or years before or after another. The start date begins as today, so the calculator also answers what date is 30, 60, or 90 days from today, and how many days until a date.
The days between two dates are also shown as weeks and days, as years, months, and days, and as business days from Monday to Friday, with U.S. federal holidays left out if you want.
How it works
Days between: the end date minus the start date. The start date counts and the end date does not, so Monday to Friday is 4 days. Turn on Count the end date too to add the last day.
Weeks and days: the days divided by 7, with the rest as days.
Years, months, and days: whole months from the start date, keeping its day of the month, then the days left. A start on the 31st uses the last day of shorter months.
Business days: the Monday to Friday days in the span. With holidays on, the 11 U.S. federal holidays are taken off, each on the weekday it is observed.
Add or subtract: years and months move the date by calendar months and keep the day of the month (clamped to the month's last day if needed); weeks and days then add 7 days and 1 day each.
Leap years follow the Gregorian calendar: every fourth year is a leap year, except century years not divisible by 400.
Which days are counted
Top: from Monday to Friday is 4 days, because the start date counts and the end date does not. Middle: with Count the end date too, Friday counts and it is 5 days. Bottom: Monday, November 23 to Monday, November 30, 2026 has 7 days and 5 weekdays; skipping federal holidays takes off Thanksgiving Day (Thursday, November 26), leaving 4 business days. Saturday and Sunday are never business days.
Quick calculator insights
Where date math goes wrong
- Counting both ends
- Monday to Friday is 4 days between, or 5 days if you count both. Say which you mean.
- Months are not 30 days
- 3 months from October 9 is January 9; 90 days is January 7.
- Month ends
- January 31 plus 1 month is February 28 (or 29), since February has no 31st.
- Holidays on weekends
- July 4, 2026 is a Saturday, so most federal employees get Friday, July 3 off.
Days in each month
Leap years follow the Gregorian rule from the U.S. Naval Observatory.
| Month | Days | Month | Days |
|---|---|---|---|
| January | 31 | July | 31 |
| February | 28 (29 in a leap year) | August | 31 |
| March | 31 | September | 30 |
| April | 30 | October | 31 |
| May | 31 | November | 30 |
| June | 30 | December | 31 |
U.S. federal holidays in 2026 and 2027
Legal public holidays under 5 U.S.C. 6103, with the day each is observed when it falls on a weekend. New Year's Day 2028 is a Saturday, so it is observed Friday, December 31, 2027.
| Holiday | 2026 | 2027 |
|---|---|---|
| New Year's Day | Thu, Jan 1 | Fri, Jan 1 |
| Martin Luther King, Jr. | Mon, Jan 19 | Mon, Jan 18 |
| Washington's Birthday | Mon, Feb 16 | Mon, Feb 15 |
| Memorial Day | Mon, May 25 | Mon, May 31 |
| Juneteenth | Fri, Jun 19 | Sat, Jun 19 (observed Fri, Jun 18) |
| Independence Day | Sat, Jul 4 (observed Fri, Jul 3) | Sun, Jul 4 (observed Mon, Jul 5) |
| Labor Day | Mon, Sep 7 | Mon, Sep 6 |
| Columbus Day | Mon, Oct 12 | Mon, Oct 11 |
| Veterans Day | Wed, Nov 11 | Thu, Nov 11 |
| Thanksgiving Day | Thu, Nov 26 | Thu, Nov 25 |
| Christmas Day | Fri, Dec 25 | Sat, Dec 25 (observed Fri, Dec 24) |
How to use this calculator
- 01Choose Add or subtract days, or Days between dates.
- 02Type the start date, or keep today.
- 03Enter the end date, or the years, months, weeks, and days to add or subtract. The 30, 60, 90, and 180 days buttons fill in the days.
- 04Read the result; business days and the other units are below it.
Inputs explained
- Calculate
- Add or subtract days finds a new date, like 90 days from today. Days between dates counts the days from one date to another.
- Start date and end date
- Type the month, day, and year, or open the calendar, which has month and year menus and a Today button. The start date begins as today.
- Count the end date too
- Off, the start date counts and the end date does not (most date calculators do this). On, both count, so the result is one day more.
- Later or earlier
- Later adds the time to the start date; earlier subtracts it.
- How much time
- Years, months, weeks, and days. The buttons set the days to 30, 60, 90, or 180.
- Count
- For Add or subtract days: calendar days, or business days that step over weekends (and federal holidays if you choose). A week of business days is 5.
- Skip U.S. federal holidays
- For Days between dates: takes the 11 federal holidays off business days, on the weekday each is observed. Built in from 2021, when Juneteenth was added.
Outputs explained
- Result
- The number of days between the dates, or the new date with its weekday.
- Weeks and days; years, months, and days
- The same span in other units.
- Business days and weekend days
- Monday to Friday days in the span, less federal holidays if you choose, and the Saturdays and Sundays.
- Calendar days and common spans
- For Add or subtract: how many calendar days the new date is from the start, and the dates 30, 60, 90, and 180 days away.
- Month end
- Shown when adding months lands on a day the month does not have, like February 31.
Worked examples
Days in 2026
- From January 1, 2026 to December 31, 2026: 364 days, counting the start date but not the end.
- With the end date counted too: 365 days, all of 2026 (not a leap year).
90 days from October 9, 2026
- October 9 to October 31 is 22 days; November adds 30 (52), December 31 (83), and 7 more days reach January 7.
- 90 days later: Thursday, January 7, 2027.
3 months is not 90 days
- October 9, 2026 plus 3 months is January 9, 2027: the same day of the month.
- October 9, 2026 plus 90 days is January 7, 2027. Months have 28 to 31 days, so 3 months is 89 to 92 days.
Adding a month to January 31
- January 31, 2026 plus 1 month: February 2026 has no 31st.
- The date moves to the last day of February: February 28, 2026.
Business days over Thanksgiving
- Monday, November 23, 2026 to Monday, November 30, 2026: 7 days, 5 of them Monday to Friday.
- Skipping federal holidays takes off Thanksgiving Day, Thursday, November 26: 4 business days.
10 business days after December 18, 2026
- Counting from Friday, December 18, skipping weekends and federal holidays: December 21, 22, 23, 24, 28, 29, 30, 31, January 4, and 5.
- Christmas Day (Friday, December 25) and New Year's Day (Friday, January 1) are skipped. Result: Tuesday, January 5, 2027.
When to use it
- Finding a deadline 30, 60, 90, or 180 days out, like a return window, notice period, or warranty.
- Counting days until a trip, a due date, or an event.
- Counting business days for shipping, a contract, or a work schedule.
- Checking how long ago something happened, in days, weeks, or months.
- Planning a project that has to skip weekends and federal holidays.
Tips
- Check whether a deadline counts the first day, the last day, or both; the Count the end date too switch shows both answers.
- For a deadline in months, use months, not 30-day blocks: 3 months from a date keeps the day of the month.
- Federal holidays are set for federal employees; your employer, school, or state may observe other days, so check yours.
- Share the link to keep the dates; it reopens the same calculation.
Limitations
- The start date counts and the end date does not, unless you turn on Count the end date too.
- Federal holidays are the 11 legal public holidays of 5 U.S.C. 6103, observed as for federal employees, from 2021 on. State holidays, company holidays, and one-time closings are not included.
- Dates are calendar dates with no time zone or time of day; hours, minutes, and seconds are whole days × 24, × 1,440, and × 86,400.
- Dates use the Gregorian calendar for every year from 1000 to 9999. It began in 1582; earlier dates were written in the Julian calendar, so a historical date may not match.
- Business days are Monday to Friday; other workweeks are not built in.
Methodology & assumptions
- Days between are the difference in whole calendar days; the end date is added only when you choose.
- Years, months, and days count whole months from the start date, clamping the day to the month's length, then the days left.
- Leap years follow the Gregorian rule as the U.S. Naval Observatory states it.
- Federal holidays and their observed days follow 5 U.S.C. 6103 and OPM's federal holidays page.
Sources
Last reviewed 2026-10-09
- U.S. Naval Observatory: Leap Years
Under the Gregorian calendar, years evenly divisible by 4 are leap years, except centurial years not evenly divisible by 400: 1700, 1800, 1900, and 2100 are not leap years; 1600, 2000, and 2400 are. The average year is 365.2425 days.
- 5 U.S. Code § 6103: Holidays (Cornell LII)
The legal public holidays: New Year's Day (January 1), Birthday of Martin Luther King, Jr. (third Monday in January), Washington's Birthday (third Monday in February), Memorial Day (last Monday in May), Juneteenth National Independence Day (June 19), Independence Day (July 4), Labor Day (first Monday in September), Columbus Day (second Monday in October), Veterans Day (November 11), Thanksgiving Day (fourth Thursday in November), and Christmas Day (December 25). A holiday on a Saturday is observed the Friday before for employees with a Monday to Friday workweek.
- U.S. Office of Personnel Management: Federal Holidays
If a holiday falls on a Saturday, for most federal employees the preceding Friday is treated as the holiday for pay and leave; if it falls on a Sunday, the following Monday (Executive Order 11582).
FAQs
How do I calculate the days between two dates?+
Subtract the start date from the end date. Count the days left in the start month, add the days in each full month between, then add the day of the end month. January 1 to March 1, 2026 is 31 + 28 = 59 days. The calculator does this for any two dates.
Does the calculator count the start date or the end date?+
It counts the start date and not the end date, as most date calculators do, so Monday to Friday is 4 days. Turn on Count the end date too to count both: 5 days.
What date is 90 days from today?+
Keep the start date as today and tap 90 days (the calculator opens on 90 days from today). From October 9, 2026, it is Thursday, January 7, 2027. The buttons also give 30, 60, and 180 days.
What date is exactly 3 months from today?+
The same day of the month, 3 months later: October 9, 2026 plus 3 months is January 9, 2027. If that month is shorter, the date moves to its last day, so November 30 plus 3 months is February 28.
Is 3 months equal to 90 days?+
Not exactly. Three months are 89 to 92 days, depending on which months: February to April is 89 days in a common year, July to September 92.
How many weeks make 90 days?+
12 weeks and 6 days, or about 12.9 weeks: 90 ÷ 7 = 12 with 6 left over.
How many days until a date?+
Keep the start date as today and set the end date. The result is the days until it, counting today but not the target day.
How do I count business days between two dates?+
Use Days between dates: the Business days line counts Monday to Friday. Turn on Skip U.S. federal holidays to take those off too. November 23 to November 30, 2026 is 5 business days, or 4 without Thanksgiving.
How do I add business days to a date?+
Choose Add or subtract days, set Count to business days, and enter the days. Weekends are stepped over, and federal holidays if you choose: 10 business days after December 18, 2026 is January 5, 2027, skipping Christmas and New Year's Day.
What happens when I add a month to January 31?+
February has no 31st, so the date moves to February's last day: February 28, 2026, or February 29 in a leap year.
Which days are U.S. federal holidays?+
New Year's Day, Martin Luther King, Jr. Day, Washington's Birthday, Memorial Day, Juneteenth, Independence Day, Labor Day, Columbus Day, Veterans Day, Thanksgiving Day, and Christmas Day. For most federal employees, a holiday on a Saturday is observed on the Friday before and one on a Sunday on the Monday after.
How many days are in a year?+
365, or 366 in a leap year. A year divisible by 4 is a leap year, except century years not divisible by 400: 2000 was a leap year, 2100 will not be.
How many days ago was a date?+
Choose Days between dates, keep the start date as today, and set the end date to the earlier date: the result gives the days and says the end is before the start.
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