Date Calculator

Date Calculator – Add or Subtract Days from a Date

Date Calculator

Add or subtract calendar days or business days from any date

Add or Subtract Days from a Date
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Date Format

Quick:
Common Day Periods from Today
PeriodCalendar DateDay of Week

How the Date Calculator Works

The date calculator adds or subtracts a given number of days from a starting date and returns the resulting calendar date. The calculation accounts for the variable lengths of months and automatically handles leap years.

Calendar Days vs Business Days

Calendar day counting includes every day of the week: Saturday, Sunday, and Monday through Friday. Business day counting skips Saturday and Sunday by default, counting only weekdays. Enabling the Saturday option adds Saturday as a counted day while still skipping Sunday.

Calendar Day Result: Start Date + N days (all days counted)
Business Day Result: Start Date + N days (weekends skipped, holidays not excluded)

Leap Year Handling

A leap year occurs every 4 years, with the exception that years divisible by 100 are not leap years unless they are also divisible by 400. For example, 2000 was a leap year but 1900 was not. This calculator correctly includes February 29 whenever a date span falls within a valid leap year.

When to Use a Date Calculator

A date calculator is useful any time you need to find a specific date a set number of days before or after another date. Common real-world uses include the following situations.

Contracts and Legal Deadlines

Many legal and commercial contracts specify deadlines in business days rather than calendar days. A 10-business-day response window starting on a Monday ends on the following Friday of the second week, not 10 calendar days later.

Shipping and Delivery

Online retailers promise delivery within a stated number of business days from the order date. If your order is placed on a Thursday and shipping takes 5 business days, the expected delivery falls on the next Thursday, not the following Tuesday.

Medical and Recovery Timelines

Doctors often specify recovery periods, follow-up appointments, or medication durations in days. Adding 14 days to a procedure date gives the follow-up window. Adding 10 days to a prescription start date identifies the end of a course of antibiotics.

Recurring Schedules

Use the calculator to build recurring event schedules. If you need to repeat a task every 90 days, calculate the next occurrence date, then use it as the new start date to find the following one, and so on.

Gardening and Planting

Seed packets list germination periods in days. Subtract the number of days from your target harvest date to find the latest planting date. For example, if a tomato variety takes 75 days and you want to harvest by August 20, you need to plant by June 6.

Date Formats Around the World

Date formats vary by country and cause considerable confusion when dates are shared across regions. Using the wrong format for a date like 05/06/2025 could be read as May 6 in the US or June 5 in Europe.

  • US format (MM/DD/YYYY): Used in the United States. The month comes first, then the day, then the four-digit year.
  • EU format (DD/MM/YYYY): Used throughout most of Europe, Australia, and many other countries. The day comes first.
  • ISO 8601 (YYYY-MM-DD): The international standard used in computing, data systems, and scientific contexts. Unambiguous and sorts correctly when alphabetically ordered.

Frequently Asked Questions

Enter today’s date in the Start Date field, select the plus operator, type 30 in the Days field, and click Calculate. The result shows the exact calendar date 30 days from now. You can also click the “+30 Days” quick button to fill the fields instantly.
Calendar days count every single day including Saturday and Sunday. Business days count only Monday through Friday. A span of 10 calendar days contains 6, 7, or 8 business days depending on where the period starts. Tick the Business Days Only checkbox to switch modes.
No. Public holidays are not automatically excluded. If your deadline or contract excludes holidays, count the number of holidays within your date range and add that number to your day total manually before calculating.
Enter your starting date, make sure the plus operator is selected, type 90 in the days field, and click Calculate. To count only weekdays, tick the Business Days Only box first. The result is the exact date 90 calendar or business days after your start.
Click the “+180 Days” quick button or enter today’s date with 180 in the days field and click Calculate. 180 calendar days is roughly 6 months, but the exact date varies because months have different lengths. The calculator gives you the precise date.
Enter the future or end date as your Start Date, select the minus operator from the dropdown, type the number of days, and click Calculate. The result is the date that many days before your starting point.
Yes. The calculator automatically accounts for leap years. If your date span crosses February 29 in a leap year, that day is correctly counted. Leap years occur every 4 years (2024, 2028, 2032, etc.) with century-year exceptions.
Three formats are supported: US format (MM/DD/YYYY), European format (DD/MM/YYYY), and ISO 8601 international format (YYYY-MM-DD). Select your preferred format using the tabs above the date field, and the placeholder will update to match.