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Date Calculator

Add or subtract any combination of years, months, weeks, and days from any starting date. See the result date, weekday, and business day count instantly.

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Date Calculator

Add or subtract time from any date

Start Date

Operation

Duration

Years

Months

Weeks

Days

How to Use the Date Calculator

Enter a start date — defaults to today, but you can pick any date.
Choose Add or Subtract — whether you want a future or past date.
Enter the duration — years, months, weeks, and/or days (combine them freely).
Click Calculate — get the result date, weekday, and business day breakdown.

Date Calculator Formula

The basic formula for adding time to a date is:

Result Date = Start Date + (Years × 365) + (Months × 30) + (Weeks × 7) + Days

Note: When adding months, the calculator adjusts for the actual number of days in each month and leap years automatically.

Common Date Calculations

Duration	Use Case	Calendar Days
7 days	One week deadline	7
14 days	Two weeks notice	14
30 days	Net 30 payment terms	30
60 days	Net 60 payment terms	60
90 days	Net 90 / probation period	90
6 months	Mid-year review	~183
1 year	Annual renewal	365 or 366

Calendar Days vs. Business Days

Calendar days count every day of the week, including weekends and holidays. When a contract says "30 days," it typically means 30 calendar days.

Business days (also called working days) count only Monday through Friday. A "30 business day" deadline is significantly longer than 30 calendar days — approximately 6 weeks.

The date calculator shows both. For holiday-aware business day calculations, use the Business Days Calculator.

? Frequently Asked Questions

How do I add days to a date?

Enter your start date, select "Add Time," type the number of days you want to add, and click Calculate. The result shows the future date along with the number of business days, weeks, and more.

Can I subtract time from a date?

Yes. Select "Subtract Time" and enter how many years, months, weeks, or days to go back. The calculator handles all the month-length and leap-year logic automatically.

Does the calculator account for leap years?

Yes. The date calculator uses JavaScript's native Date object, which correctly handles leap years, month lengths, and daylight saving time transitions.

What is the difference between calendar days and business days?

Calendar days count every day including weekends and holidays. Business days count only Monday through Friday, excluding weekends (but not public holidays, which vary by country).

Can I add years and months together?

Yes. You can combine years, months, weeks, and days in a single calculation. For example, add 1 year, 2 months, and 15 days all at once.