Date Calculator

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Calculate exactly how many days, weeks, months, and years are between any two dates. Includes working days.

Days Between Dates

0 days

Weeks0
Months (approx)0
Years (approx)0
Working Days0

📐 Formula

Days Between = |Date2 − Date1| ÷ 86,400,000 milliseconds. Working days ≈ Total days × (5/7)

How to Use the Date Calculator

1

Choose calculation type

Select 'Days between dates' to find the gap between two dates, or 'Add/subtract days' to find a date that is a specific number of days from a starting point.

2

Enter the start and end dates

Input dates using the date picker. For legal or contract deadlines, verify whether the start date itself counts as day 0 or day 1 — this varies by jurisdiction and contract.

3

Toggle calendar vs business days

Business days (Monday–Friday, excluding weekends) are used for legal deadlines, contract terms, and financial settlements. Calendar days count every day including weekends and holidays.

4

Note the day of the week

The result includes the weekday name — useful when scheduling around weekends or when a deadline falls on a holiday.

How Date Calculations Work

Every date corresponds to a Julian Day Number — a continuous count of days since January 1, 4713 BC. Computers subtract two Julian Day Numbers to find the exact number of days between dates, handling leap years, varying month lengths, and calendar reforms automatically. A leap year occurs every 4 years (with exceptions: century years must also be divisible by 400 — 2000 was a leap year; 1900 was not).

Business Day Calculations: Why They Differ

Legal and financial contexts frequently specify business days rather than calendar days. A 30-business-day deadline is approximately 6 calendar weeks — but the exact end date depends on which weekdays fall within the range. Most US legal rules exclude weekends but do not automatically exclude federal holidays; whether a holiday counts depends on the specific rule or contract. The Federal Rules of Civil Procedure (Rule 6) define a business day as any day that is not Saturday, Sunday, or a federal legal holiday. When accuracy matters, verify the applicable rule and consider which holidays fall within the period.

Common Date Calculation Use Cases

Contract expiry and notice periods; court filing deadlines; age verification for legal purposes (e.g. is this person 18 today?); project timelines and milestone planning; warranty and insurance policy durations; payroll and billing cycles; calculating days until an event; and determining how many days of a lease or subscription have elapsed. For legal matters, always confirm the counting method — inclusive vs exclusive of the start date, and calendar vs business days — before relying on any date calculation tool.

Sources & Methodology

Calculations are based on the most current publicly available data from authoritative government and industry sources:

Frequently Asked Questions

Subtract the earlier date from the later date in milliseconds, then divide by 86,400,000 (milliseconds per day). This calculator handles all the complexity for you.
A standard year has 260–262 working days (52 weeks × 5 days), minus public holidays. In the US, with 10 federal holidays, the typical number is about 250 working days per year.
Calendar days count every day including weekends and holidays. Working days (business days) only count Monday–Friday, excluding public holidays. Always clarify which type is meant in contracts or deadlines.
Enter today's date and your target date in the calculator above. The result accounts for leap years automatically. Common uses: days until a deadline, event, or expiration. The US averages 261 working days per year after excluding weekends — the calculator can show business days only if needed.
There are exactly 52 weeks and 1 day in a standard year (365 days), or 52 weeks and 2 days in a leap year (366 days). This is why your birthday advances by one day of the week each year (two days after a leap year). For project planning, most businesses use 52 weeks as the working year.