Day Counter

How the Day Counter Works

This day counter finds the number of days between two dates, or the number of days until or since a single target date. It turns every date into a whole day number, subtracts one number from the other and then splits the span into business days, weekend days, US federal holidays, weeks, months and years. Every result comes with the arithmetic, so you can check it by hand.

Dates are handled as whole calendar days in Coordinated Universal Time (UTC), not as clock times. A day that loses or gains an hour for daylight saving time still counts as exactly one day. That removes the classic off by one error that appears when a 23 hour day is divided by 24 and rounded down.

The default result leaves out the end date, the convention used for ages and for deadlines counted in days after an event. The 358 day example equals 51 weeks and 1 day, or 0.98 of an average Gregorian year of 365.2425 days. When the end date comes before the start date the counter shows a negative number, while the Days until or since tab always reports a positive count labeled until or since.

Including or Excluding the End Date: Why Calculators Differ by One Day

Most disagreements between day calculators come from one choice: whether the last date counts. An exclusive count measures the gap between two dates, which equals the number of midnights you pass. An inclusive count lists every date from the first through the last, so it is always exactly one higher.

Spreadsheets mix conventions too. In Excel, subtracting one date cell from another gives the exclusive count, while the NETWORKDAYS function counts both the start and the end date. Microsoft's own example returns 110 workdays from October 1, 2012 to March 1, 2013, which matches an inclusive count; an exclusive count of the same weekdays gives 109.

Two other causes of a one day gap are time zones and holiday lists. A tool that subtracts timestamps taken in local time can lose a day across a daylight saving change, and a business day count built on a company holiday list will differ from one built on federal holidays.

How to Count Days Between Two Dates Manually

Month by month method

1. Count the days left in the start month after the start date.
2. Add the full length of every month in between.
3. Add the day of the month of the end date.
4. Add 1 if the end date should be counted.

From March 15, 2026 to August 9, 2026, March leaves 31 − 15 = 16 days, then April adds 30, May 31, June 30 and July 31, and August adds 9. The total is 16 + 30 + 31 + 30 + 31 + 9 = 147 days, or 148 days with the end date included.

Day of year method

For two dates in the same year, convert each one to its day of the year with the month table further down and subtract. March 15 is 59 + 15 = day 74 of 2026 and August 9 is 212 + 9 = day 221, so 221 − 74 = 147 days. For dates in different years, take the days left in the first year, add the day of year of the second date, and add 365 or 366 for every full year in between. July 4, 2025 is day 185, which leaves 365 − 185 = 180 days in 2025; adding day 1 of 2026 gives 181 days to January 1, 2026.

Julian day number method

Astronomers avoid month lengths entirely by numbering every day in one continuous count. The US Naval Observatory publishes the Fliegel and van Flandern formula, which turns a Gregorian date into a Julian day number (JDN) using whole number division that drops any fraction.

The method works across centuries and leap years with no lookup table. The calculator uses an equivalent count, days since January 1, 1970, and shows both numbers in Your calculation. The Naval Observatory gives Julian day number 2,440,588 for January 1, 1970, which is why the two numbers always differ by 2,440,588.

Business Days and Working Days Between Dates

Business days are the counted dates that fall in your working week, minus holidays. The counter supports Monday to Friday, Monday to Saturday and Sunday to Thursday weeks. It can also remove US federal holidays on the dates observed by federal employees who work Monday to Friday.

Federal law, 5 U.S.C. 6103, lists 11 legal public holidays. Five fall on fixed dates and six fall on a set weekday. When a fixed date holiday lands on a Saturday it is observed on the Friday before, and when it lands on a Sunday it is observed on the Monday after. The table lists the 2026 dates, which match the schedule published by the Office of Personnel Management (OPM).

Worked example for the first quarter of 2026: January 1 through March 31 with both ends counted is 90 days. Of those, 64 are weekdays and 26 are weekend days. New Year's Day, Martin Luther King Jr. Day and Washington's Birthday fall inside the range, so the result is 64 − 3 = 61 business days.

Observed dates matter near weekends. From Monday, June 29 to Friday, July 10, 2026, both ends counted, there are 12 days and 10 weekdays. Independence Day is a Saturday that year, so the holiday moves to Friday, July 3 and the count is 9 business days, not 10. The same rule can move a holiday into the previous year: January 1, 2028 is a Saturday, so it is observed on Friday, December 31, 2027.

Holiday rules are applied from 1971, when the Monday holiday law took effect, with Martin Luther King Jr. Day from 1986, Veterans Day back on November 11 from 1978 and Juneteenth from 2021. Inauguration Day, a holiday every fourth year only for federal employees in the Washington, DC area, is not removed, and neither are state holidays, bank holidays or company closures.

Days in Each Month, Days in a Year and Leap Year Rules

The table gives the length of every month and the number of days before each month starts. Add the date to the days before figure to get the day of the year: August 9, 2026 is 212 + 9 = day 221.

A common year has 365 days, which is 52 weeks and 1 day, or 8,760 hours. A leap year has 366 days, 52 weeks and 2 days, or 8,784 hours. Because 2026 starts on a Thursday, Thursday occurs 53 times and every other weekday 52 times, which gives 261 weekdays and 104 weekend days.

In the Gregorian calendar a year divisible by 4 is a leap year, except century years, which are leap years only when divisible by 400. The US Naval Observatory lists 1700, 1800, 1900 and 2100 as common years and 1600, 2000 and 2400 as leap years. The rule adds 97 leap days every 400 years, so the average year is 365.2425 days, the figure the Decimal years tile divides by.

Leap days change day counts. February 15 to March 15 is 28 days in 2027 but 29 days in 2028, because February 29, 2028 falls in between. The Leap days tile shows how many February 29 dates your range contains. The calculator accepts years from 1583, the first full year of the Gregorian calendar, to 9999.

Days From a Date: 30, 60, 90 and 180 Day Deadlines

To find the date a set number of days after a start date, add the days to its day number and convert back. Day 0 is the start date itself, so 30 days after January 1 is January 31, not January 30. The results list these dates for your own start date under Dates after the start.

A 90 day period that starts on March 1, 2026 ends on May 30, 2026, and the counter returns exactly 90 days between those two dates. A 280 day span from January 1, 2026 ends on Thursday, October 8, 2026, exactly 40 weeks later. Deadlines that land on a weekend or holiday are often moved to the next business day by the rule that governs them, so check the weekday shown in the table. To add months or years instead of days, use the Date Calculator.

Understanding Your Result

The large number is the answer to your question: calendar days by default, or business days when you choose them. The line under it repeats both dates with their weekdays and says whether the end date was counted, so you can confirm that the inputs are the ones you meant. The bar shows what share of the counted dates are business days, weekend days and removed holidays.

The calendar card restates the span as years, months and days, plus weeks and days. Months are counted forward from the earlier date; when the day of the month does not exist, such as January 31 plus one month, the count stops at the last day of the shorter month. The tiles give hours and minutes for short projects, decimal years for interest and rate calculations, and the number of leap days.

For related questions, the Age Calculator gives exact age from a birth date, the Time Calculator and Hours Calculator handle durations inside a day, and the Time Zone Calculator converts clock times between cities.

Frequently Asked Questions

Sources & References

• U.S. Office of Personnel Management. Federal Holidays, 2026 and 2027 holiday schedules and the Saturday and Sunday observance rule. opm.gov
• Legal Information Institute, Cornell Law School. 5 U.S. Code § 6103, Holidays (list of legal public holidays, Saturday observance, effective dates of the 1968, 1975, 1983 and 2021 amendments). law.cornell.edu
• U.S. Naval Observatory. Leap Years (Gregorian leap year rule, 97 leap days in 400 years, 365.2425 day average year). aa.usno.navy.mil
• U.S. Naval Observatory. Converting Between Julian Dates and Gregorian Calendar Dates (Fliegel and van Flandern formula, JD 2440588 for January 1, 1970). aa.usno.navy.mil
• Royal Museums Greenwich. Which years are leap years and can you have leap seconds? (leap year rule and hours in a leap year). rmg.co.uk
• Microsoft Support. NETWORKDAYS function (Excel working day count and example results). support.microsoft.com
• MDN Web Docs. Date.UTC() (UTC day arithmetic used by the calculator). developer.mozilla.org

Results are informational estimates of calendar and business day counts and do not replace the deadline rules in a contract, court rule or employer policy. Every number on this page was recomputed with the same code the calculator runs. Holiday data reviewed: 2026.