Date Calculator

Add or subtract days, weeks, months, or years from any date. Find the exact difference between two dates in days, weeks, months, and years. Includes business days and day of the week.

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Add or Subtract from a Date

Start Date

Operation

Amount

Unit

Days Between Two Dates

From Date

To Date

Date Result

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Days

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Weeks

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Months

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Years

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Business Days

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Weekends

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Day of Week

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Days in Each Month

Month	Days	Month	Days	Month	Days
January	31	May	31	September	30
February	28 / 29	June	30	October	31
March	31	July	31	November	30
April	30	August	31	December	31

February has 29 days in leap years (divisible by 4, except centuries unless divisible by 400). Total: 365 days/year or 366 in leap years.

US Federal Holidays (2026)

Holiday	2026 Date	Day
New Year's Day	January 1	Thursday
MLK Jr. Day	January 19	Monday
Presidents' Day	February 16	Monday
Memorial Day	May 25	Monday
Independence Day	July 4	Saturday
Labor Day	September 7	Monday
Columbus Day	October 12	Monday
Veterans Day	November 11	Wednesday
Thanksgiving	November 26	Thursday
Christmas Day	December 25	Friday

Date Calculations Explained

Date arithmetic is more complex than it appears because months have different lengths (28-31 days), leap years add an extra day, and time zones can shift the calendar date. "30 days from March 15" is April 14, but "1 month from March 15" is April 15 — a subtle but important distinction for contracts, deadlines, and project planning.

Business day calculations exclude weekends (Saturday and Sunday) and are essential for payroll, shipping estimates, legal deadlines, and project management. A "30 business days" deadline is typically 6 calendar weeks (42 calendar days), not 30 calendar days. This calculator computes both.

For age calculations down to the day, use our Age Calculator. For pregnancy timelines, the Due Date Calculator uses this same date math with Naegele's Rule. For tracking work hours across dates, see the Hours Calculator.

Frequently Asked Questions

How many days are in a year?

A common year has 365 days. A leap year has 366 days. Leap years occur every 4 years (2024, 2028, 2032), except century years unless divisible by 400 (2000 was a leap year, 1900 was not). The average year is 365.2425 days, which is why we need the leap year system.

How do I calculate business days?

Count only Monday through Friday between two dates, excluding weekends. This calculator does this automatically. Note that federal holidays are not automatically excluded — business day conventions vary by industry and jurisdiction.

What is 90 days from today?

Use the "Add or Subtract" tool above, set today's date, add 90 days. Common deadlines: 30 days ≈ 1 month, 90 days ≈ 3 months, 180 days ≈ 6 months, 365 days = 1 year. Note that "3 months" and "90 days" may land on different dates depending on month lengths.

How do I find what day of the week a date falls on?

Enter any date in either calculator tool and the result will show the day of the week. This is useful for planning events, checking if a holiday falls on a weekend, or determining work schedules for future dates.

Is there a difference between "30 days" and "1 month"?

Yes. "30 days from January 15" is February 14. "1 month from January 15" is February 15. The distinction matters for contracts, billing cycles, and legal deadlines. This calculator handles both — use "Days" for exact day counts and "Months" for calendar month intervals.

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