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Day Calculator

Calculate the number of days between two dates, count only business days (Mon-Fri), find the day of the week for any date, and add or subtract days. Free online tool.

Last revised 13 September 2026

By Team GlobalCalqulate · About our editorial standards

Date Calculation

Calculation Type

Start Date

End Date

Days to Add

Days to Subtract

For Add/Subtract, skips weekends when landing on the result date. Days Between always shows both business days and weekend days in the breakdown.

Days Between

364

Business days: 260, Weekends: 104

Methodology

Formula:: Days between dates
Content last updated:: September 2026
Scheduled re-verification:: September 2027

Calculation type: Exact calculation.

Formula & methodology

Formula used

Days between dates

days = (end − start) ÷ 86,400,000 ms

The difference between two dates in whole days.

Adding or subtracting days

result = start date ± n days

Calendar arithmetic that rolls over month and year boundaries and accounts for leap years.

Business days

count each day in the range, excluding Saturdays and Sundays

Weekends are stepped over one day at a time rather than estimated as a fraction of the total.

Variable definitions

Symbol	Meaning	Unit
start	Start date. the first date in the range	date
end	End date. the last date in the range	date
n	Days to add or subtract. the offset applied to the start date	days

Step-by-step calculation

1. Choose the mode
Days between two dates, or a date a given number of days away.
2. Enter the dates
Business-day counting can be switched on for the range mode.

Limitations

Business days exclude weekends only. Public holidays are not deducted — use the working days calculator for that.
Dates are interpreted in the browser's local time zone.
Daylight-saving transitions make some days 23 or 25 hours long; whole-day counts are unaffected, but hour-level arithmetic is.

This page is educational. It applies the formula described above to the figures you enter and shows the arithmetic behind the result. The output is only as good as the inputs and the assumptions listed here, and it is general information rather than advice about your particular situation.

Help & FAQs

Frequently Asked Questions

Clear answers to common questions to help you use this calculator confidently.

How do business days differ from calendar days?

Tap to view the answer

Calendar days include weekends. Business days count only Monday-Friday. 10 calendar days from Monday is about 1.5 weeks later. 10 business days from Monday is exactly 2 weeks later. Use business days for work deadlines, calendar days for event countdowns.

How do I calculate days until a specific date?

Tap to view the answer

Enter today as the start date and your target as the end date. Select 'Days Between.' You'll see total days, business days, and weekend days remaining. The day of the week for your target date is also shown.

Does the calculator account for leap years?

Tap to view the answer

Yes. Leap years (divisible by 4, except century years not divisible by 400) are correctly handled. February has 29 days in leap years. 2024 was a leap year; the next is 2028.

Can I add business days (not calendar days) to a date?

Tap to view the answer

Yes — in Add/Subtract mode, enable "Count Only Business Days" and the calculator skips weekends when landing on the result date. For example, adding 10 business days to a Monday lands on the Monday after next.

Does the calculator account for public holidays?

Tap to view the answer

No. Business days count Monday-Friday only. Public holidays vary by country and year. For project deadlines involving holidays, add buffer days or manually check holiday calendars for your region.

Need more help? Contact support or email globalcalqulate@gmail.com

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How to Use This Calculator

Choose What to Calculate

Pick 'Days Between' to count days between two dates, 'Add/Subtract' to find a future or past date, or 'Day of Week' to check which weekday a date falls on.

Enter Your Dates or Number of Days

For 'Days Between,' enter both dates. For add/subtract, enter a starting date and how many days to add or remove.

Toggle Business Days

Enable business days to count only Monday-Friday (useful for project deadlines, work contracts, and service-level agreements).

Review Your Results

See total calendar days, business days, weekend days, and the day of the week — all at once.

Understanding Your Results

Total Days
Every calendar day between two dates, including weekends. The count is exclusive of the start date and inclusive of the end date.
Business Days
Weekdays only (Monday through Friday). The standard count for project timelines, contract durations, and work schedules.
Day of the Week
Which weekday a date falls on — determined using the Gregorian calendar with leap year correction.
Add/Subtract Days
Shifts a date forward or backward by a specified number of calendar days, useful for deadline and milestone calculations.

Key Tips

✓
Business days exclude weekends but do not account for public holidays — add a buffer for holiday closures.
✓
When calculating project deadlines, business days give a realistic estimate of working time, not calendar time.
✓
The add/subtract feature works with business days — add 10 business days to a Monday and you land on a Monday two weeks later.
✓
Leap years are automatically accounted for in all date calculations.

How Day Calculations Work

Counting Days Between Two Dates

The calculator counts every calendar day from the start date (exclusive) to the end date (inclusive). For business days, it filters to Monday-Friday only. For example, January 1 to January 5 includes 4 total days: Jan 2 (Fri), Jan 3 (Sat), Jan 4 (Sun), Jan 5 (Mon). Business days would count 2 (Fri and Mon). The calculation accounts for leap years by recognizing February 29 in leap years (years divisible by 4, but not century years unless divisible by 400).

Business Days vs Calendar Days — When Each Matters

Calendar days are appropriate when counting down to a fixed event (a wedding, a vacation, a product launch). Business days are appropriate for work-related timelines: project deadlines, contract durations, invoice payment terms (Net 30 typically means 30 calendar days, but some contracts specify business days), and service-level agreements. The key difference is that 10 business days spans two calendar weeks, while 10 calendar days is just over one week.

Adding and Subtracting Days

The add/subtract function moves a date forward or backward by the specified number of calendar days. Add 90 days to January 1 to find the date 90 days later (around April 1, depending on leap years). This is useful for: calculating contract end dates, finding due dates for invoices or deliverables, counting statutory notice periods, and planning events a specific number of days out. The calculator shows both the result date and its day of the week.

Day of the Week — How It's Calculated

The weekday for any date is determined by counting total days from a known anchor (January 1, 1900 = Monday) to the target date, then using modulo 7 (remainder after dividing by 7) to get the day. The calculation correctly accounts for all leap years and Gregorian calendar reforms. You can find the weekday for any date from 1900 forward, including historical dates and far-future dates.

Leap Year Rules

A year is a leap year if it's divisible by 4, except century years, which are leap years only if also divisible by 400. So 2024 is a leap year (divisible by 4, not a century year), 2000 was a leap year (divisible by 400), but 1900 was not (divisible by 100 but not 400). Leap years add a 366th day (February 29), which shifts the day-of-week and day-of-year calculations for every date after that point in the year.

Common Day-Counting Mistakes

Assuming inclusive/exclusive counting matches your intuition — this calculator counts the start date as excluded and the end date as included, so June 1 to June 14 returns 13 days, not 14. Confirm which convention a contract or deadline uses before relying on a day count for it. Treating calendar days as business days — 14 calendar days spanning two weekends is only 10 business days, not 14. Forgetting that business-day counts here exclude weekends only, not public holidays, which vary by country and year — add a manual buffer for holiday closures. Using ambiguous date formats (03/04/2026 means March 4 in the US and April 3 in most of the rest of the world) — entering dates through the date picker avoids this ambiguity entirely.

How Day of the Week Is Determined

Every date maps to exactly one weekday, calculated by counting the total number of days from a fixed reference point and taking the remainder after dividing by 7. This calculation correctly threads through leap years and varying month lengths, so it works the same way for a date in 1950 as for one in 2050 (Gregorian calendar rules apply from 1582 onward).

Limitations of This Calculator

This calculator works in calendar dates only — it does not account for time zones or specific clock times, so a deadline tied to '5 PM in a specific time zone' needs that conversion done separately. Business-day counts exclude weekends (Saturday/Sunday) but not public holidays, since holiday calendars vary by country and year. Historical dates before the Gregorian calendar's adoption in 1582 are not supported.

Formula & methodology

Formula used

Days between dates

days = (end − start) ÷ 86,400,000 ms

The difference between two dates in whole days.

Adding or subtracting days

result = start date ± n days

Calendar arithmetic that rolls over month and year boundaries and accounts for leap years.

Business days

count each day in the range, excluding Saturdays and Sundays

Weekends are stepped over one day at a time rather than estimated as a fraction of the total.

Variable definitions

Symbol	Meaning	Unit
start	Start date. the first date in the range	date
end	End date. the last date in the range	date
n	Days to add or subtract. the offset applied to the start date	days

Step-by-step calculation

1. Choose the mode
Days between two dates, or a date a given number of days away.
2. Enter the dates
Business-day counting can be switched on for the range mode.

Limitations

Business days exclude weekends only. Public holidays are not deducted — use the working days calculator for that.
Dates are interpreted in the browser's local time zone.
Daylight-saving transitions make some days 23 or 25 hours long; whole-day counts are unaffected, but hour-level arithmetic is.

Calculator inputs

Date Calculation

Your results

Methodology

Formula & methodology

Formula used

Days between dates

Adding or subtracting days

Business days

Variable definitions

Step-by-step calculation

Limitations

How do business days differ from calendar days?

How do I calculate days until a specific date?

Does the calculator account for leap years?

Can I add business days (not calendar days) to a date?

Does the calculator account for public holidays?

Related calculators

More everyday calculators

Calculator inputs

Date Calculation

Your results

Methodology

How to Use This Calculator

Example: Days Between Jan 1 and Dec 31, 2026

Understanding Your Results

Key Tips

How Day Calculations Work

Counting Days Between Two Dates

Business Days vs Calendar Days — When Each Matters

Adding and Subtracting Days

Day of the Week — How It's Calculated

Leap Year Rules

Common Day-Counting Mistakes

How Day of the Week Is Determined

Limitations of This Calculator

Formula & methodology

Formula used

Days between dates

Adding or subtracting days

Business days

Variable definitions

Step-by-step calculation

Limitations

How to Use This Calculator

Example: Days Between Jan 1 and Dec 31, 2026

Understanding Your Results

Key Tips

How Day Calculations Work

Counting Days Between Two Dates

Business Days vs Calendar Days — When Each Matters

Adding and Subtracting Days

Day of the Week — How It's Calculated

Leap Year Rules

Common Day-Counting Mistakes

How Day of the Week Is Determined

Limitations of This Calculator