How do I calculate the number of days between two dates?

Enter a start date and end date in the calculator. It instantly shows the difference in days, weeks, months, and years. For example, from January 1 to March 31 is 89 days (90 in a leap year).

Does the date calculator include the start and end date?

By default, the end date is not counted. Enable ''Include end date in count'' to add one extra day so both the first and last day are included in the result.

How do I count business days between two dates?

Enable ''Exclude weekends'' in the advanced options. The calculator subtracts all Saturdays and Sundays, returning only Monday-to-Friday working days.

Can I calculate how many days until a future date?

Yes. Set today as the start date and your target date as the end date. The result shows exactly how many days, weeks, and months remain until that date.

What is the difference between calendar days and business days?

Calendar days count every day including weekends. Business days count only Monday through Friday. A two-week period has 14 calendar days but only 10 business days.

How many days are between two dates in different years?

The date calculator handles multi-year spans accurately, accounting for leap years. For example, from January 1, 2020 to January 1, 2025 is exactly 1,827 days (5 years including one extra leap day).

How do leap years affect date difference calculations?

Leap years add one extra day (February 29) every four years, with exceptions for century years not divisible by 400. The calculator automatically accounts for every leap year in the span, ensuring precise results for multi-year date ranges.

Can I use this calculator for legal or contract deadlines?

Yes, but verify the counting convention required. Legal deadlines often use inclusive counting (counting both the start and end day) — enable ''Include end date'' for this. For court-specific rules, always confirm with a legal professional.

What is the difference between a fiscal year and a calendar year for date calculations?

A calendar year runs January 1 to December 31. A fiscal year is any 12-month accounting period a company or government designates — it may start in April, July, or October. This calculator works with calendar dates; for fiscal period calculations, adjust your start and end dates accordingly.

Date Calculator

Calculate the number of days, weeks, months, and years between any two dates.

Start Date

End Date

Advanced options

Include end date in count

Exclude weekends

Reviewed by

Marcus Webb

Software Engineer & Developer Tools Specialist

· BSc Computer Science, University of Washington· Senior Engineer at Cloudflare (2018–2023)· Open-source contributor to Temporal API proposals

About the Date Difference Calculator

The date difference calculator uses precise Gregorian calendar arithmetic to count the exact number of days, weeks, months, and years between any two dates. Unlike simple subtraction, accurate date math must account for varying month lengths (28–31 days), leap years (every 4 years, with exceptions for century years), and the direction of the difference (past or future).

The calculator converts both dates to a consistent epoch timestamp, computes the absolute difference in milliseconds, then converts to the requested units. For month and year breakdowns, it applies Gregorian calendar rules rather than approximating — because treating all months as 30 days would introduce errors of up to 5 days per year.

How Date Difference Is Calculated

Days

The absolute difference between the two dates in 24-hour periods. Leap years are accounted for automatically — a leap year adds exactly one extra day (February 29) to multi-year spans.

Weeks & Remaining Days

Total days divided by 7 gives complete weeks. The leftover days (0–6) are shown separately, making it easy to see ''how many full weeks plus extra days'' the period spans.

Months & Years

Calculated by comparing year and month components directly. A span from January 31 to March 31 is exactly 2 months — the calculator does not approximate by dividing days by 30.

Business Days

When ''Exclude weekends'' is enabled, every Saturday and Sunday in the period is subtracted from the total. The result reflects Monday–Friday working days only.

Common Use Cases

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Project management — Calculate how many days remain until a deadline, or how long a completed project actually took from kick-off to delivery.
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Age verification — Confirm that a person has reached the required age (18, 21, 25) for a contract, election, or age-restricted service as of a specific date.
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Legal & regulatory deadlines — Statute of limitations periods, contract notice requirements, and regulatory response windows are all counted in exact calendar days.
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Financial calculations — Bond maturity, loan terms, interest accrual periods, and subscription billing cycles all depend on precise day counts between dates.
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Event planning — Count the exact days until a wedding, anniversary, conference, or product launch — and share the link with others.