Days Between Dates Calculator
Example 1
A project manager needs to calculate the number of days between 1 January 2026 and 15 March 2026 for a project timeline.
Solution
January has 31 days, so from 1 January to 31 January is 30 days (excluding the start date).
February 2026 is not a leap year (2026 is not divisible by 4), so it has 28 days.
March contributes 15 days (from 1 March to 15 March).
Answer
73 days between 1 January 2026 and 15 March 2026.
Example 2
A student wants to know how many days remain until their graduation on 20 May 2027. Today is 1 November 2026.
Solution
From 1 November to 30 November: 29 days (excluding start date). December: 31 days.
January 2027: 31 days, February 2027: 28 days (not a leap year), March: 31 days, April: 30 days, May 1–20: 20 days.
Answer
200 days remaining until graduation on 20 May 2027 from 1 November 2026.
Example 3
A contractor needs to calculate the duration of a construction project starting on 5 March 2026 and ending on 15 September 2026. How many calendar days and business days (approx) are in this period?
Solution
From 5 March to 31 March: 26 days. April: 30 days. May: 31 days. June: 30 days. July: 31 days. August: 31 days. September 1–15: 15 days.
Approximate business days: 194 × 5/7 = 138.6, roughly 139 weekdays excluding weekends.
Answer
194 calendar days (approximately 139 business days) between 5 March 2026 and 15 September 2026.
Example 4
A legal filing has a 90-day deadline starting on 20 December 2025. The rules count only business days and exclude federal holidays (assume 1 January and 25 December are holidays). What is the filing deadline?
Solution
Start: 20 December 2025. Total calendar window: 20 Dec to 20 March 2026 is roughly 90 days.
December 2025: 11 remaining days (21–31). January 2026: 31 days. February 2026: 28 days. March 2026: 20 days = 90 total days.
Subtract weekends: 90 calendar days contain approximately 26 weekend days, leaving 64 potential business days.
Subtract 2 holidays (25 Dec, 1 Jan): 62 business days. Need 90 business days, so extend by 28 more calendar days.
Answer
The filing deadline falls approximately 118 calendar days from 20 December 2025, around 16 April 2026. Always verify business day counts with your legal calendar.
Published:
Updated:
References
- [1]National Institute of Standards and Technology, The Gregorian Calendar - NIST Time and Frequency Division. https://www.nist.gov/pml/time-and-frequency-division
- [2]International Swaps and Derivatives Association, ISDA Day Count Conventions, 2006.
- [3]United States Naval Observatory, Leap Years - Astronomical Applications Department. https://aa.usno.navy.mil
- [4]United States Courts, Federal Rules of Civil Procedure Rule 6 - Computing and Extending Time.
Glossary
- Date difference – The amount of calendar time elapsed between two dates, measured in years, months, weeks, days, hours, minutes, and seconds. Date differences are computed using calendar boundaries rather than fixed time intervals.
- Calendar day – A 24-hour period from midnight to midnight as defined by the Gregorian calendar. Calendar days include all days of the week, including weekends and public holidays.
- Leap year – A year with 366 days instead of 365, occurring every four years except for century years not divisible by 400. The extra day (February 29) compensates for the Earth’s orbital period of approximately 365.2422 days.
- Month – A division of the calendar year that varies in length from 28 to 31 days. The Gregorian calendar has 12 months: January (31), February (28 or 29), March (31), April (30), May (31), June (30), July (31), August (31), September (30), October (31), November (30), and December (31).
- Year – The time it takes for the Earth to complete one orbit around the Sun, approximately 365.2422 days. The Gregorian calendar represents this as either 365 days (common year) or 366 days (leap year).
- Week – A unit of time equal to seven consecutive calendar days, starting on Sunday or Monday depending on cultural convention. The ISO standard defines Monday as the first day of the week.
- Business day – A day on which normal business operations are conducted, typically Monday through Friday, excluding weekends and public holidays. Business day counts vary by jurisdiction due to different public holiday calendars.
- Weekday – Any day of the week that is not a weekend day. In most countries, weekdays are Monday through Friday. Weekdays are used for business operations, school schedules, and most commercial activities.
- Weekend – The two-day period at the end of the week, typically Saturday and Sunday in most Western countries. Weekend days are excluded from business day counts and often have different operating hours for businesses and services.
- Time zone – A region of the globe that observes a uniform standard time for legal, commercial, and social purposes. Date differences at the calendar-day level are not affected by time zones, but elapsed hours may differ when events occur in different time zones.
How to Use?
- 1
Select the start date
Choose the earlier of the two dates from the date picker. This is the date from which the calculator begins counting.
- 2
Select the end date
Choose the later date from the second date picker. This must be on or after the start date. The calculator counts up to but does not include this date.
- 3
Review the primary duration result
The Exact Duration field shows the span in years, months, and days. Below it, you will find the breakdown into total days, weeks, months, years, hours, minutes, and seconds.
- 4
Check the business days estimate
The Business Days field shows the approximate number of weekdays (Monday through Friday) within the range. This estimate does not deduct public holidays, which vary by jurisdiction.
- 5
Explore the reference content
Scroll below the calculator to find the days-per-month table, notable date range examples, Gregorian calendar explanation, and detailed guidance on professional applications.
- 6
Use the examples to verify your understanding
The worked examples section shows real date ranges with their calculated results. Compare these against your own calculations to ensure you are using the correct date format.
Frequently Asked Questions
The calculator uses the full Gregorian calendar date-difference algorithm, which correctly handles leap years (years divisible by 4, except century years not divisible by 400). If your date range includes 29 February of a leap year, the calculator counts that day in the total. For example, from 1 March 2023 to 1 March 2024 returns 366 days because 2024 is a leap year and 29 February 2024 falls within the range.
The calculator uses exclusive counting, which means it counts the full 24-hour periods between the two dates. From 1 January to 2 January is 1 day. The start date is not counted, and the end date is not counted. This is the standard convention for date differences in most contexts. If your situation requires inclusive counting (counting both dates), add 1 to the total days result.
Calendar days include every day of the week, including Saturdays, Sundays, and public holidays. Business days (also called working days) exclude Saturdays and Sundays. This calculator estimates business days by counting the number of weekdays (Monday through Friday) in the date range. It does not deduct public holidays because those vary by jurisdiction. For a rough conversion, multiply your calendar day count by 5/7 to get an approximate business day count.
The calculator uses calendar dates without time zone adjustment. The day count between two dates remains the same regardless of time zone, because a calendar date represents a full 24-hour period. However, if you need to know the exact elapsed hours across time zones, the start and end events may occur at different local times on the same calendar dates. For most legal and business purposes, date-level precision is sufficient.
The calculator uses the Gregorian calendar, which was introduced in October 1582. Dates before 15 October 1582 are not supported because the Julian calendar was in use before that date. The Gregorian reform also skipped 10 days (4 October 1582 was followed by 15 October 1582). For historical research, note that different countries adopted the Gregorian calendar at different times. Great Britain and its colonies adopted it in 1752, skipping 11 days (2 September was followed by 14 September).
The Exact Duration field breaks the date span into full years, remaining months, and remaining days. It first counts the number of full years between the dates (checking whether the anniversary has passed). Then it counts the number of full months remaining after those years. Finally it counts the remaining days. For example, from 10 April 2024 to 5 September 2026 gives 2 years, 4 months, and 26 days. This structured breakdown matches how humans naturally describe date spans.
The total months count represents full calendar months between the dates. A span from 15 January to 14 February returns 0 months because a full calendar month boundary (from the 15th of one month to the 15th of the next) has not been crossed. The same span returns 30 days. For spans shorter than a month, the months output is 0 and the days output shows the actual day count. This is mathematically correct: one month is not the same as 30 days.
Yes, the calculator gives you the actual calendar days between two dates, which is the numerator in many day count fractions. For US Treasury bonds (actual/actual convention), divide the day count by the actual days in the coupon period. For corporate bonds (30/360 convention), you need to convert the day count using the 30-day month convention, where each month is treated as 30 days regardless of actual month length. Always verify which day count convention applies to your specific bond or derivative contract.
The business day count excludes Saturdays and Sundays only. It does not deduct public holidays because holiday calendars vary by country, state, and even by employer policy. If you need a business day count that excludes specific holidays, subtract the number of public holidays that fall within your date range from the calculator’s business day result. For a more precise estimate, check your jurisdiction’s public holiday calendar for the relevant year.
A result of 0 months with positive days means the date span is shorter than one full calendar month. For example, from 20 June to 5 July is 15 days. The month boundary (from the 20th to the 20th) has not been crossed, so the months count is 0. The days count reflects the actual elapsed time. This is the correct mathematical representation of the date difference and is consistent with how the Gregorian calendar defines month boundaries.
Yes. The calculator shows total hours, total minutes, and total seconds below the main duration result. These are derived from the total days count: hours = days × 24, minutes = hours × 60, seconds = minutes × 60. These calculations assume 24-hour days and do not account for daylight saving time transitions, which can add or subtract one hour on the transition dates. For most purposes, these unit conversions provide a useful approximation of the span in smaller time units.
Set today’s date as the start date and the future date as the end date. The calculator will show the exact number of days (and all other units) between now and that future date. For example, if today is 15 March 2026 and you want to know how many days until 25 December 2026, enter those two dates and the calculator returns 285 days. The weeks, months, and hours breakdowns give you additional ways to understand the remaining time.
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