Date Calculator: Add and Subtract to a Date

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Below is a date calculator, where you can choose to add or subtract years, months, weeks, or days. Enter a beginning date, select if you'd like to 'add' or 'subtract', then the number of each unit of time and we'll do the math for you.

Date Calculator

Using the Date Calculator

To use the date calculator, merely enter your start date, function, and units of time. Here are all the inputs:

  • Before Date: Enter the beginning date to start the math
  • Add to or Subtract from Date?: Choose the function to use, to add from the start date or subtract
  • Years: The number of years to add or subtract
  • Months: The number of months to add or subtract
  • Weeks: The number of weeks to add or subtract
  • Days: The number of days to add or subtract

After you've filled out the inputs to your satisfaction, hit the blue 'Calculate Date' button. You'll quickly see an output:

  • Calculated Date: The result of the date calculation using your units of time

How do you calculate the days?

Pretty simply – we do the math linearly. We add the years first, then months, weeks, and finally days.

If you're curious, we're using Moment.js behind the scenes.

Do you factor in leap years?

Yes, the date tool does account for leap years. However, unless you're using days and weeks heavily you probably won't run into them too often.

Months and years abstract away the days and weeks inside so you likely won't even notice them.

Our Other Dates and Time Calculators

Useful calculator, right? We've got a bunch more for your fun:

Also, see our other finance and econ calculators. See you around!



PK started DQYDJ in 2009 to research and discuss finance and investing and help answer financial questions. He's expanded DQYDJ to build visualizations, calculators, and interactive tools.

PK lives in New Hampshire with his wife, kids, and dog.

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DQYDJ may be compensated by our partners if you make purchases through links. See our disclosures page. As an Amazon Associate we earn from qualifying purchases.
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