How to add days to a date
Adding days to a date seems simple — count forward from the start — but month boundaries make it tricky. If you add 30 days to January 15, you land on February 14 in a regular year (and the same in a leap year). Add 30 days to January 31 and you land on March 2 (or March 1 in a leap year). This calculator handles all those edge cases automatically, including month-length variations, year rollovers, and the extra day in February during leap years. It supports days, weeks, months, and years as units, and works equally well for adding time forward or subtracting time backward from any date between 1900 and 2100.
Practical uses for date arithmetic
Date arithmetic is used constantly in professional and personal life. Businesses calculate payment due dates (net-30, net-60 terms), subscription renewal dates, trial period end dates, and warranty expirations. Healthcare providers track medication schedules, prenatal milestones, and follow-up appointment windows. Legal teams compute statutory deadlines and filing windows. Project managers find milestone dates by adding sprint lengths to start dates. Students work out when assignments are due. Anyone planning a trip counts forward to find departure and return dates. This calculator handles the math so you don't have to count on your fingers.
Frequently asked questions
What date is 30 days from today?
Enter today's date as start, choose "Add" and "30 days", then click Calculate. The result will be the exact date 30 days from now, accounting for varying month lengths. For example, 30 days from March 15 is April 14.
What date is 90 days from today?
Use the same method with 90 days. This is a common business calculation — many contracts and warranties have 90-day terms. Because months vary in length, 90 days is not exactly 3 months; the calculator gives you the precise calendar date.
How do I add 30 days to a specific date?
Enter your target date as the start date, select "Add" and enter 30 in the amount field with "days" as the unit, then click Calculate. The exact result date is shown immediately along with its day of the week and week number.
What date is 90 days from a given date?
Enter your start date, select "Add", enter 90, and choose "days". The calculator correctly handles month boundaries — 90 days from January 1 is April 1 in a non-leap year and March 31 in a leap year.
How do I subtract months from a date?
Select "Subtract" from the operation dropdown, enter the number of months, and choose "months" as the unit. The calculator handles edge cases like subtracting 1 month from March 31, which correctly gives February 28 (or 29 in a leap year).
How do I calculate a project deadline?
Enter your project start date, select "Add", enter the project duration, and choose the appropriate unit (days, weeks, or months). The result shows the deadline date along with the day of the week — useful for spotting if a deadline falls on a weekend.
What date is 100 days from today?
Use the same method with 100 days. Because months have different lengths, you cannot simply count 3 months — the calculator gives you the precise date. 100 days from January 1 lands on April 11 in a regular year.
What date is 6 months from now?
Enter today as start, choose "Add" and "6 months". The result correctly handles cases like adding 6 months to August 31 (the result is February 28/29 in the following year) and other end-of-month edge cases.