Does it handle leap years correctly?

Yes. By using JavaScript’s built-in Date handling, the calculator automatically accounts for February 29 in leap years and the varying number of days in each month.

How do I count business days instead of calendar days?

This tool counts calendar days only. To count business days, you would need to layer on rules for weekends and holidays, which this calculator does not currently support. You can still use the output as a starting point and then manually adjust for non-working days.

Can I make the result inclusive of both start and end dates?

Yes. The raw output is an exclusive day difference. If your policy or use case counts both the start and end date, simply add 1 to the result (as long as the end date is on or after the start date).

What happens if the end date is before the start date?

Depending on the implementation, you may see a negative day count. For most planning scenarios, you will want the start date to be on or before the end date to get a positive, forward-looking difference.

everyday calculator

Date Difference Calculator

Calculate days between two dates for deadlines, projects, or travel planning.

Results

Days between: 55.00

How to use this calculator

Enter the start date (year, month, and day) you want to count from—for example, the date a contract begins or the day you leave home.
Enter the end date you want to count to—for example, the day something is due or the day you return.
Run the calculation; we compute the difference between the two dates in milliseconds and convert it into days.
Review the number of days between the two dates as an exclusive difference (start day 0, end day not counted).
If your scenario requires an inclusive count—where both the start and end dates are counted—add 1 to the result.

Inputs explained

Start date: The beginning date for your calculation. This might be the date a project kicks off, a rental period starts, or a bill is issued. The calculator treats this as day 0 when computing the day difference.
End date: The final date you want to measure to. For example, a due date, return date, or milestone. For a positive result, the end date should be the same as or after the start date.

How it works

You enter a calendar start date and a calendar end date using year, month, and day.

Behind the scenes, we create JavaScript Date objects for both dates, which automatically handle month lengths and leap years.

We subtract the start date from the end date to get a difference in milliseconds.

We then divide by the number of milliseconds in a day (1000 × 60 × 60 × 24) to convert that difference into days.

The result is the number of whole days from the start date up to (but not including) the end date. If you prefer inclusive counts, you can add one day to the result.

Formula

Conceptually, the calculator does the following:\n\n1. Convert the start and end inputs into Date objects.\n2. Compute the difference in milliseconds: diffMs = endDate − startDate.\n3. Convert to days: days = diffMs ÷ (1000 × 60 × 60 × 24).\n4. Report the day difference as an exclusive count; add 1 manually if you need inclusive days.

When to use it

Checking project timelines or contract deadlines by counting how many days fall between a start date and a delivery date.
Planning travel, vacations, or hotel stays by seeing how many nights fall between check-in and check-out dates.
Counting days between medical appointments, medication cycles, or habit streaks.
Comparing time gaps between events—for example, time between paydays, invoices, or recurring tasks.

Tips & cautions

Decide upfront whether you need an exclusive (start not counted, end not counted) or inclusive (both counted) day count and adjust the result accordingly.
For long spans that cross years or leap years, let the calculator handle the complexity—manually counting February 29s is error-prone.
Keep your year, month, and day entries consistent (for example, use 1–12 for months and 1–31 for days) and double-check that you didn’t swap month and day for ambiguous dates.
If you are coordinating across time zones, anchor your dates to a specific zone or to UTC to avoid confusion about start and end days for international events.
The calculation assumes valid Gregorian calendar dates and does not handle historic calendar reforms or non-Gregorian calendars.
It operates on whole days only—time of day (hours, minutes) is ignored, so partial days are not reflected in the result.
It does not factor in business days, weekends, or holidays; it simply counts calendar days between the two dates.
User input errors (such as reversed start/end dates or swapped month/day values) will change the result, so always verify your entries for important deadlines.

Worked examples

Example 1: Jan 10 to Mar 5 (non-leap year)

Start date = January 10; end date = March 5.
The calculator counts all days from Jan 10 up to (but not including) Mar 5.
Result ≈ 54–55 days depending on the specific year (the tool uses the exact calendar for the year you enter).

Example 2: Feb 1 to Feb 28 in a non-leap year

Start date = February 1; end date = February 28 in a year without Feb 29.
Days between = 27 (Feb 1 to Feb 28 exclusive).
If you wanted to count both Feb 1 and Feb 28 inclusively, you would add 1 to get 28 days.

Example 3: Crossing a leap day

Start date = February 1, 2024; end date = March 1, 2024.
Because 2024 is a leap year, February has 29 days.
The calculator automatically includes Feb 29 in the count when computing the days between those dates.

Deep dive

Use this date difference calculator to instantly find the number of days between two dates for deadlines, trips, projects, or habit tracking.

Enter any start and end date to see the day count, with leap years handled automatically so you don’t have to manually scan calendars or worry about February 29.

Great for planners, project managers, and everyday users who want quick, reliable date math without spreadsheet formulas.

FAQs

Does it handle leap years correctly?: Yes. By using JavaScript’s built-in Date handling, the calculator automatically accounts for February 29 in leap years and the varying number of days in each month.
How do I count business days instead of calendar days?: This tool counts calendar days only. To count business days, you would need to layer on rules for weekends and holidays, which this calculator does not currently support. You can still use the output as a starting point and then manually adjust for non-working days.
Can I make the result inclusive of both start and end dates?: Yes. The raw output is an exclusive day difference. If your policy or use case counts both the start and end date, simply add 1 to the result (as long as the end date is on or after the start date).
What happens if the end date is before the start date?: Depending on the implementation, you may see a negative day count. For most planning scenarios, you will want the start date to be on or before the end date to get a positive, forward-looking difference.

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This date difference calculator is a convenience tool for counting calendar days between two dates. It does not account for business day rules, legal holidays, or jurisdiction-specific deadline calculations and is not legal, financial, or scheduling advice. For critical deadlines—such as court dates, contract obligations, or medical schedules—always confirm timing with an official calendar, applicable rules, and qualified professionals.