How many days until Christmas?

Christmas Day is December 25. Use our live Days Until Christmas countdown to see the exact number of days remaining, updated every second in your local time zone.

How many days are there between two dates?

Enter any start and end date in our Days Between Dates calculator to get the exact number of days, including or excluding the end date. The calculation runs locally in your browser.

How many days until New Year?

New Year's Day is January 1. Our Days Until New Year countdown shows the exact time remaining, counting down every second in your local time zone.

How many weeks are between two dates?

Use our Weeks Between Dates calculator to get the number of full weeks between any two dates, ideal for planning, projects, and deadlines.

Are these date calculators free and private?

Yes. All HowManyDays.app calculators are completely free with no limits. Every calculation happens locally in your browser — we never see, store, or transmit the dates you enter.

➕ Add or Subtract Days to a Date

Pick a start date, then add or subtract a number of days to find the exact resulting date.

Need to know what date falls exactly 90 days from today, or which day was 28 days ago? The Add or Subtract Days calculator answers instantly. Choose any start date, enter a positive number of days to move forward or a negative number to go back, and the tool returns the exact date — including the correct month length and leap years.

This is one of the most common date calculations in everyday life. Project managers use it to set milestones and deadline reminders. Businesses use it to calculate invoice due dates, trial periods, and guarantee windows. Students and freelancers use it to plan assignment deadlines and payment schedules. Instead of flipping through a calendar and counting days by hand, you get a precise answer in a second.

For example, adding 90 days to January 15 gives April 15, and subtracting 28 days from March 5 gives February 5. Leap years are handled automatically, so adding 30 days to a date in late January correctly rolls into February with 29 days in a leap year.

Start Date

Days (use − to subtract)

How Does the Calculation Work?

The tool reads the start date and the number of days you entered, then converts them into a JavaScript Date object set to midnight UTC. Adding or subtracting a number of days is done with setUTCDate, which lets the JavaScript engine handle month lengths and leap years automatically — you never have to manually work out how many days each month has.

A negative value subtracts days, letting the tool move backward in time just as easily as forward. The result is then formatted in a clear, readable form showing the weekday and full date, so you know not just the date but which day of the week it falls on.

Practical Examples

Adding 90 days to January 15, 2025 lands on April 15, 2025 — a typical 90-day warranty or payment window. Subtracting 28 days from March 5, 2025 gives February 5, 2025, useful for a 28-day notice period or billing cycle. And on a project starting August 1, adding 120 days points to November 29, rolling correctly across the September and October month boundaries.

Edge Cases and Common Pitfalls

The main pitfall people hit is forgetting that months have different lengths. Adding 30 days to a date late in the month does not always land on the same numerical day of the next month — it depends on how many days that month has. This tool avoids the trap by letting the date engine resolve the correct calendar day.

Leap years are handled automatically: adding 30 days from January 29 in a leap year lands on February 28, while in a common year it lands on February 28 as well — the engine always respects the real number of days in February. Business users should also note that this tool counts calendar days, not business days; if you need weekdays only, use the separate Workdays Counter.

Business and Personal Uses

Businesses use this calculation constantly: 30-day payment terms, 14-day return windows, 60-day subscription trials, and 90-day warranty periods are all defined in days rather than calendar months. Knowing the exact end date matters for contracts and cash flow. On a personal level, it's handy for planning trips, medication refills, fitness streaks, or simply knowing what date falls 100 days from today.

Try also:

Days Between Dates Weeks Between Dates Workdays Counter Days Until Date Leap Year Checker Day of the Week Finder

Frequently Asked Questions

How do I add days to a date?

Enter your start date, type a positive number in the days field (for example 90), and click Calculate. The tool returns the exact date 90 calendar days later, accounting for the correct number of days in each month.

How do I subtract days from a date?

Enter your start date, then type a negative number in the days field (for example −28) before clicking Calculate. The tool moves backward in time and shows the exact date 28 days before your start date.

Does this calculator handle leap years correctly?

Yes. The tool uses the browser's built-in date engine, which knows exactly how many days are in each month of each year. Adding days across a leap-year February rolls over correctly into March.

Is this calendar days or business days?

This tool counts calendar days, including weekends and holidays. If you need only working days between two dates (excluding Saturdays and Sundays), use our Workdays Counter instead.

What is 90 days from today?

Enter today's date and add 90 days to get the exact answer. Because months have different lengths, the result depends on your start date — the tool calculates it precisely for you rather than relying on a rough rule of thumb.

Written by Aren Breur — IT professional with 30+ years of experience and founder of HowManyDays.app.

Every tool on this site is built, tested, and maintained by hand by Aren to be accurate, fast, and privacy-friendly — all calculations run locally in your browser. Found an error or have feedback? Contact us or email aren2connect@gmail.com. Read more about this site.