About This Tool
Whether you need to count down to an important event, calculate a project deadline, or determine how many business days fall between two dates, our free Date Calculator provides all the answers in one place. It handles the most common date arithmetic operations that come up in both personal and professional life.
Enter a start date and end date to instantly see the difference expressed in days, weeks, months, and years. The tool also calculates the number of business days (Monday through Friday) between your selected dates, which is essential for project planning, legal deadlines, and payroll calculations where only working days count.
Beyond date differences, the calculator lets you add or subtract a specified number of days from your start date. This is perfect for determining future deadlines (such as "what date is 90 days from today?") or looking back at past dates (such as "what date was 30 days ago?"). Both the forward and backward results are displayed simultaneously for convenience.
Date calculations might seem simple, but they are surprisingly complex when you factor in months with different lengths, leap years, and the distinction between calendar days and business days. This calculator handles all of these nuances automatically, delivering accurate results that you can rely on for planning, scheduling, and record-keeping.
Key Features
- Calculate the exact number of days, weeks, months, and years between any two dates
- Business day calculation that excludes weekends (Saturday and Sunday)
- Add or subtract any number of days from a starting date to find future or past dates
- Handles leap years and variable month lengths for precise results
- Clean dual-purpose interface combining date difference and date arithmetic in one tool
How this tool works
Methodology reviewed 2026-07-11The tool takes the absolute millisecond difference between two dates for elapsed days, derives whole weeks by division by seven, approximates months with 30.44 days and years with 365.25 days, and adds or subtracts entered calendar days from the start date. Its weekday loop iterates inclusively from the earlier through the later date and excludes Saturday and Sunday only.
Worked example
From a Monday to the following Monday there are seven elapsed calendar days. A simple weekday count may include five business days, but it will not automatically remove a national, state, religious, or company holiday.
How to interpret it: Confirm whether an endpoint should be inclusive for your deadline. Contracts and agencies can define business days differently, and daylight-saving changes can make raw hour differences misleading even when calendar dates are correct.
Assumptions
- Dates are interpreted using the browser calendar and local timezone.
- Weekday counting is inclusive of both endpoints, unlike the elapsed-day difference.
- Business days mean Monday through Friday with no holiday or closure list.
Limitations
- Start/end order is discarded because the difference is absolute, and legal deadlines may use different inclusion rules.
- The 30.44-day month and 365.25-day year are average-length approximations rather than calendar-component differences.
Sources
Sources explain the standard or planning method; they do not endorse Free Toolset or verify individual results.
Frequently Asked Questions
How are business days calculated?
Business days include Monday through Friday and exclude Saturday and Sunday. This calculator counts every weekday between your start and end dates. Note that it does not account for public holidays, which vary by country and region. For critical business deadlines, verify holiday schedules separately.
Does the calculator account for leap years?
Yes, the calculator correctly handles leap years. When adding or subtracting days, February 29 is included in leap years. The day count between dates also accurately reflects the actual number of days in each month and year within the range.
What is the difference between calendar days and business days?
Calendar days include every day (Monday through Sunday), while business days only count weekdays (Monday through Friday). For a typical week, there are 7 calendar days but only 5 business days. This distinction matters for deadlines, shipping estimates, and contractual time periods.