Day Calculator

How to use the day calculator

1. Pick a start date. It starts on today’s date.
2. Choose whether to add or subtract.
3. Enter any mix of years, months, weeks and days. The new date and its weekday appear right away.

Common date calculations

Question	What to enter
What date is 90 days from today?	Today, Add, 90 days
What was the date 6 weeks ago?	Today, Subtract, 6 weeks
When is 30 days after a contract date?	Contract date, Add, 30 days
What is 18 months from a start date?	Start date, Add, 18 months

How days are counted

Adding 1 day moves to the next calendar date, so 90 days from January 1 is April 1 in a normal year (March 31 in a leap year). The start date itself is not counted, which matches how most deadlines, notice periods and due dates work.

Months do not all have the same number of days, so “add 1 month” moves to the same day number in the next month. If that day does not exist (for example, February 30), the calculator uses the last day of the month instead.

Business days

This calculator counts every calendar day, including weekends. If a deadline is given in working days, use the business day calculator, which skips weekends.

Frequently asked questions

How do I find the date 100 days from today?

Leave the start date as today, choose Add and enter 100 days. The result shows the date and the day of the week.

Does the calculator include the start date?

No. Adding 1 day to Monday gives Tuesday. If your rule counts the start day as day 1, subtract one day from your total.

Are leap years handled?

Yes. February 29 is included in leap years, so results are exact for any year.

Can I mix weeks and days?

Yes. Fill in any combination of years, months, weeks and days, and they are all applied together.

How many weeks is 90 days?

90 days is 12 weeks and 6 days, or about 12.86 weeks.