Introduction
The Date Add Calculator lets you add or subtract time from any date. Pick a start date, then enter the years, months, weeks, days, hours, and minutes you want to add or take away. The tool does the math for you and shows the exact result right away. It also shows a clear step-by-step breakdown so you can see how the answer was found.
You can also switch to business day mode. This skips weekends and holidays when counting days. You get to choose which US holidays to exclude, and you can even add your own custom holidays. This is helpful for planning work deadlines, project timelines, or delivery dates. If you need to count only business days between two known dates, our dedicated tool can help with that as well.
Whether you need to find a future date, look back at a past date, or count only working days, this calculator makes date arithmetic simple and fast.
How to Use Our Date Add Calculator
Enter a start date and choose how much time to add or subtract. The calculator will show you the exact future or past date and time, along with a step-by-step breakdown of how it got the answer.
Start Date & Time: Pick the date and time you want to start from. It defaults to right now.
Operation: Choose "Add" to move forward in time or "Subtract" to move backward.
Years: Enter the number of years to add or subtract.
Months: Enter the number of months, from 0 to 11.
Weeks: Enter the number of weeks to add or subtract.
Days: Enter the number of days to add or subtract.
Hours: Enter the number of hours, from 0 to 23.
Minutes: Enter the number of minutes, from 0 to 59.
Business Days Toggle: Turn this on if you only want to count work days. This skips weekends and disables the hours and minutes fields.
Business Day Rules: When business days mode is on, choose whether to skip weekends only or skip both weekends and holidays.
US Holidays to Exclude: Check or uncheck common US holidays you want to skip when counting business days.
Custom Holidays to Exclude: Add your own holidays by typing a name and picking a month and day. Click "Add more" for extra rows.
Press Calculate to see your result or Reset to clear all fields and start over.
What Is Date Addition and Subtraction?
Date addition is when you start with a date and move forward in time by a set amount. Date subtraction is the opposite — you move backward. For example, if today is January 10 and you add 5 days, you get January 15. If you subtract 5 days, you get January 5.
This sounds simple with small numbers, but it gets tricky fast. Months have different lengths. February has 28 or 29 days. Some months have 30, and others have 31. When you add years, you also have to think about leap years. Doing this math by hand is easy to mess up, especially when you mix years, months, weeks, days, hours, and minutes all at once.
How Date Arithmetic Works
When you add time to a date, there is an order that matters. Years and months are added first because they change the calendar position. Then weeks and days are added, since those are fixed lengths of time. Finally, hours and minutes are applied. Each step builds on the result of the step before it. For a more general approach to combining or converting time values, you can also use our Add Time Calculator.
One important detail is end-of-month clamping. If you start on March 31 and add 1 month, you would land on April 31 — but April only has 30 days. So the result gets clamped to April 30. This rule keeps results valid no matter what date you start from.
What Are Business Days?
Business days are the days of the week when most people work: Monday through Friday. Saturdays and Sundays are skipped. When you count in business days, you only count weekdays. This is useful for shipping estimates, project deadlines, legal due dates, and work schedules.
You can also exclude holidays from the count. For example, if a deadline is 10 business days away and there is a holiday in between, that holiday does not count as a business day. This calculator lets you pick which U.S. holidays to skip and even add your own custom holidays.
When Is This Useful?
People use date addition and subtraction every day without thinking about it. You might need to find a due date that is 90 days from now. You might want to know what date falls exactly 1 year and 3 months after a contract was signed. Employers count business days to figure out payroll deadlines. Courts use business days to set filing deadlines. If you need to measure the span between two dates rather than adding time to one, try our Date Duration Calculator. For tracking how long ago a specific event occurred, the Days Since Calculator is another handy option. This calculator handles all of that math for you in seconds.