How to Use This Date Calculator
Add or subtract days, weeks, months, or years from any dateโor compare two dates and count workdays before a deadline. This calculator handles it all.
Choose the Right Mode
- Add/Subtract Time:Use this mode when you already know the starting date and want to move forward or backward by a set number of years, months, weeks, or days.
- Difference Between Dates:Use this mode when you want to know how far apart two dates are, either as an exact span or as a total day count.
- Weekend exclusion:Turn this on when you need a weekday count instead of counting every calendar date.
- Holiday exclusion:Choose a supported holiday calendar when observed holidays should be removed from the final workday count.
Calendar Days vs. Business Days
A calendar-day count includes every date in the range. A business-day count starts with that calendar span, then removes excluded weekends and observed holidays. In simple form: If your boss asks how many working days are left before a project deadline, that is the number you need, not the raw calendar count.
How the Day Count Is Calculated
Under the hood, the calculator turns each date into a timestamp and compares the difference in milliseconds: That matters because calendar math is messier than it looks. Months do not all have the same length, leap years add an extra day to February, and daylight saving transitions can make a clock day feel longer or shorter. By working from actual calendar dates first, then applying exclusions, the calculator avoids the common mistakes people make when they try to count dates by hand.
Holiday Calendars and Observed Dates
When you turn on holiday exclusions, the calculator can skip observed holidays from the US, UK (England & Wales), or Canada. That matters because many workplaces do not close on the literal holiday date when it lands on a weekend; they close on the observed weekday instead. If you are counting shipping days, approval days, or office workdays, the observed calendar is usually the one that matters.
Date Calculator FAQ
How do I add or subtract days from a date?
Use the "Add/Subtract Time" mode: pick your starting date, enter the number of years, months, weeks, or days you want to add or subtract, then click Add or Subtract. The result shows the new date and weekdayโideal for deadlines, notice periods, or "what date is 90 days from today?" style questions.
Why is my business-day count different from my manual count?
Most manual counts miss one of three things: whether the start or end date is included, whether weekends are removed, and whether observed holidays are moved to a nearby weekday. This calculator applies those rules consistently, so the business-day result can differ from a quick count on a wall calendar.
How do I calculate 90 days from today?
Use "Add/Subtract Time," keep today as the base date, enter 90 in the days field, and click Add. The calculator will return the exact future date along with the weekday, which is useful when you need to answer questions like "what date is 90 days from today?" or "what date is 3 months from now?"
How do I count business days between two dates?
Open "Difference Between Dates," enter the start date and end date, then turn on "Exclude Weekends" to remove Saturdays and Sundays. If you also need official holidays removed, turn on "Exclude Holidays" and choose the appropriate calendar. The business-day result updates automatically, so you can count working days between two dates without doing it by hand.
What happens if the end date lands on a weekend or holiday?
The calendar-day result does not change just because the end date falls on a weekend or holiday. But if you turn on weekend or holiday exclusions in "Difference Between Dates," those dates are removed from the business-day count, so the working-day total may be lower than the raw calendar span.
Does daylight saving time affect the date count?
Not for the main day-based results. This calculator works from local calendar dates, so daylight saving transitions do not change the day count itself. If you need exact clock-hour differences across a DST switch, use a time-based calculator instead of a date-only one.
What happens when I add one month to a date near the end of the month?
Month-based date math is tricky because months are not all the same length. This calculator follows the JavaScript calendar rules used by the browser, so end-of-month cases such as January 31, February 29, or adding across short months are handled automatically rather than by assuming every month has 30 days.