How do you calculate the days between two dates?

Convert both dates to a day number and subtract the earlier from the later. This calculator uses exact calendar dates, so every month length and leap day is handled for you.

Is the end date included in the count?

Not by default. From 1 January to 2 January is 1 day. Tick Include End Date to add 1 day, which counts both the start and the end day.

How are business days counted?

Business days are the Monday to Friday dates inside the range. Public holidays are not removed because they differ by country and region.

How are leap days counted?

A leap day is a 29 February that falls inside your range. The tool counts each one, and also shows how many leap years your range touches.

Does it handle century years like 1900 and 2100?

Yes. It follows the Gregorian rule: a year divisible by 100 is a leap year only if it is also divisible by 400, so 1900 and 2100 are not leap years.

Days Between Two Dates Calculator - Leap Year Difference

Days Between Two Dates Calculator & Leap Year Difference

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Pick a start date and an end date to count calendar days, business days, weekend days and every leap day in between.

✓ Dates loaded from a shared link. Edit them to recalculate.

Start Date

End Date

Include End Date (+1 day)

Choose a start date and an end date to count the days.

Day Count

Total Calendar Days-

Business Days (Mon-Fri)-

Weekend Days-

Business days -Weekend days -

Leap Year Details

Leap Days (29 Feb)-

Leap Years Spanned-

Weeks and Days-

Exact Difference

Years-

Months-

Days-

Other Units

Total Weeks-

Total Hours-

Total Minutes-

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What Is a Days Between Dates Calculator?

A days between dates calculator tells you how many days separate two calendar dates. People use it for project deadlines, contract terms, pregnancy and travel planning, countdowns, loan periods and checking how long ago something happened.

This version goes further than a simple subtraction. It separates business days from weekend days, counts every leap day (29 February) inside the range, shows how many leap years the range touches, and gives the exact difference in years, months and days.

How to Use This Calculator

Choose a Start Date and an End Date. If the end is earlier, the dates are swapped for you.
Tick Include End Date (+1 day) if both the first and last day should be counted.
Press Calculate Milestone, or change any field and the results refresh on their own.
Read the calendar days, business days, weekend days, leap days and exact difference.
Copy the link or the result summary to save or share it.

Mathematical Formula & Calculation Mechanics

Total days: N = (End day number - Start day number) + 1 if the end date is included. Day numbers come from exact calendar dates, so month lengths are always correct.

Business days: take the full weeks first: floor(N / 7) × 5. Then check each of the remaining N mod 7 days, starting from the weekday of the start date, and add one for every Monday to Friday. Weekend days = N - business days.

Leap days: a year is a leap year if it divides by 4, except century years, which must divide by 400. The tool counts each 29 February that falls inside the counted days, and separately counts the leap years among the calendar years the range touches.

Exact difference: subtract year, month and day, borrowing the real length of the previous month when the day goes negative. Public holidays are not removed from business days.

Step-by-Step Worked Example

Question: How many days are there from 1 January 2024 to 1 January 2025?

Step 1: 2024 is a leap year, so the range holds 366 days. That is 52 whole weeks plus 2 extra days.

Step 2: 1 January 2024 is a Monday, so the 2 extra days are Monday and Tuesday. Business days = 52 × 5 + 2 = 262, and weekend days = 366 - 262 = 104.

Step 3: The leap day, 29 February 2024, falls inside the range, so the leap-day count is 1.

Step 4: The exact difference is 1 year, 0 months and 0 days. If the end date were included, the total would be 367 days and business days would be 263.

Comprehensive Reference Table: Day Counts for 40 Intervals

Each interval starts on Monday, 1 January 2024 and ends before the same date later (end date not included). Other start dates give slightly different business-day and leap-day counts.

Date Milestone Interval	Total Calendar Days	Business Days Count	Weekend Days	Elapsed Leap Years Count
1 week	7	5	2	0
2 weeks	14	10	4	0
3 weeks	21	15	6	0
4 weeks	28	20	8	0
1 month	31	23	8	0
2 months	60	44	16	1
3 months	91	65	26	1
4 months	121	87	34	1
5 months	152	110	42	1
6 months	182	130	52	1
7 months	213	153	60	1
8 months	244	175	69	1
9 months	274	196	78	1
10 months	305	219	86	1
11 months	335	240	95	1
1 year	366	262	104	1
18 months	547	391	156	1
2 years	731	523	208	1
3 years	1,096	784	312	1
4 years	1,461	1,045	416	1
5 years	1,827	1,305	522	2
6 years	2,192	1,566	626	2
7 years	2,557	1,827	730	2
8 years	2,922	2,088	834	2
9 years	3,288	2,350	938	3
10 years	3,653	2,610	1,043	3
12 years	4,383	3,131	1,252	3
15 years	5,479	3,915	1,564	4
18 years	6,575	4,697	1,878	5
20 years	7,305	5,219	2,086	5
21 years	7,671	5,480	2,191	6
25 years	9,132	6,524	2,608	7
30 years	10,958	7,828	3,130	8
35 years	12,784	9,132	3,652	9
40 years	14,610	10,436	4,174	10
50 years	18,263	13,045	5,218	13
60 years	21,915	15,655	6,260	15
65 years	23,742	16,960	6,782	17
75 years	27,394	19,568	7,826	19
100 years	36,524	26,090	10,434	24

Calendar & Business-Day Reference Facts

Benchmark	Value	Why It Matters
Days in a common year	365	52 weeks and 1 extra day
Days in a leap year	366	52 weeks and 2 extra days
Leap year rule	Divisible by 4, except century years not divisible by 400	1900 and 2100 are not leap years; 2000 and 2024 are
Leap years in a 400-year cycle	97	Makes the average year 365.2425 days
Days in a 400-year cycle	146,097	Exactly 20,871 whole weeks
Average days per month	30.44	365.2425 days divided by 12
Average weeks per year	52.18	365.2425 days divided by 7
Weekdays in a common year	260 or 261	Depends on the weekday of 1 January
Weekdays in a leap year	260 to 262	Depends on the weekday of 1 January
Standard weekend	Saturday and Sunday	Used in the US, UK, Canada and Australia; some Middle Eastern countries use Friday and Saturday

Legal deadlines such as notice periods can be counted differently in each jurisdiction. Confirm the exact rule with the official source before relying on a day count.

Frequently Asked Questions

Question	Answer
How do you calculate the days between two dates?	Convert both dates to a day number and subtract the earlier from the later. This calculator uses exact calendar dates, so every month length and leap day is handled for you.
Is the end date included in the count?	Not by default. From 1 January to 2 January is 1 day. Tick Include End Date to add 1 day, which counts both the start and the end day.
How are business days counted?	Business days are the Monday to Friday dates inside the range. Public holidays are not removed because they differ by country and region.
How are leap days counted?	A leap day is a 29 February that falls inside your range. The tool counts each one, and also shows how many leap years your range touches.
Does it handle century years like 1900 and 2100?	Yes. It follows the Gregorian rule: a year divisible by 100 is a leap year only if it is also divisible by 400, so 1900 and 2100 are not leap years.

Days between dates calculator - Leap Year Difference