This free Date Calculator answers the three most common date questions in one place: how many days between two dates, exactly how old you are, and what date falls a certain number of days from today. Whether you are counting down to a deadline, figuring out your age for a form, planning a 90-day challenge, or checking a contract expiry date, this tool gives you the answer instantly without opening a spreadsheet or counting a calendar by hand.

The tool is split into three tabs, each built for a specific task. The Date Difference tab calculates the gap between any two dates — it does not matter which date is earlier. You get the total days, total weeks, total hours, and a precise year/month/day breakdown, which is what you need when someone asks "how many days is 3 years and 2 months?" or when a lease says "expiry is 365 days from signing." The swap button lets you reverse start and end in a click.

The Age Calculator tab is purpose-built for birthdate calculations. Enter any date of birth and it shows your current age in years, months, and days, plus your total age in days lived, total weeks, and approximate hours. It also tells you the day of the week you were born on, your Western zodiac sign, and how many days remain until your next birthday. These details come up more often than you'd expect — in job applications, government forms, medical records, trivia, and birthday milestone planning.

The Add / Subtract tab lets you jump forward or backward in time from any starting date. You can type any number of days or use the quick presets: Yesterday, −1 week, +1 week, −30 days, +30 days, +60 days, +90 days, −1 year, and +1 year. The result date is shown with the full day name. This tab is what you need when a warranty runs 90 days from purchase, a probation period is 6 months, a payment is 30 days net, or you want to know what date 100 days from today is.

Date arithmetic is tricky because months have different lengths, leap years add a day, and crossing year boundaries is easy to miscalculate by hand. February has 28 days in common years and 29 in leap years. Some months have 30 days, others 31. If you try to manually calculate "how many days from March 15 to November 8" you would need to count March (16 days remaining), then April (30), May (31), June (30), July (31), August (31), September (30), October (31), and 8 days of November — 238 days total. The calculator does this in milliseconds with no risk of error.

Common uses include: counting days until an event (birthday, exam, wedding, deadline), checking how long a project or subscription has been running, verifying a contract or lease expiry, calculating age for forms or insurance, checking how many days left in a fiscal quarter, finding what date is exactly 90 days after a medical procedure or warranty purchase, and planning milestones like 1000 days together or 10,000 days of age.

All calculations happen in your browser. No dates, inputs, or results are sent to a server. The tool works offline once the page loads and remembers your last inputs in local storage.

Features

Date difference in total days, total weeks, years/months/days breakdown, and total hours
Age calculator showing years, months, days, total days lived, total weeks, and approximate hours
Days until next birthday shown automatically in the Age tab
Day of the week and zodiac sign for any birthdate
Add or subtract any number of days from any start date
Quick presets: Yesterday, ±1 week, ±30 days, ±60 days, ±90 days, ±1 year
Swap button to reverse start and end dates instantly
Handles leap years and variable month lengths correctly
Copy result to clipboard
Saves last inputs in browser storage
Runs entirely in your browser — no data sent to a server

How to Use

1
Pick a tabChoose Date Difference (gap between two dates), Age Calculator (age from a birthdate), or Add / Subtract (jump forward or backward from a date).
2
Enter your datesUse the date pickers. For Date Difference, enter start and end dates in any order — the tool always shows the positive difference. For Age, enter your birthdate.
3
Read the resultsThe hero number shows the most useful metric (total days or age in years). The 6-metric grid breaks it down into all representations simultaneously.
4
Use quick presets for Add/SubtractIn the Add / Subtract tab, use the preset buttons (Yesterday, +1 week, +30 days, +90 days, +1 year, etc.) to jump to common intervals without typing.
5
Copy the resultClick Copy next to the summary row to copy the result to your clipboard.

Common Use Cases

Count days between two dates

Enter any two dates in the Date Difference tab and instantly see total days, weeks, and a year/month/day breakdown.

Calculate your exact age

Enter your birthdate and see your age in years, months, days, total days, weeks, and hours — plus days until your next birthday.

Find what date is X days from today

Use Add / Subtract with quick presets (+30, +60, +90 days) to jump forward from today for deadlines, warranties, and payment terms.

Count days until an event

Set today as start and your event as end in Date Difference to get the exact countdown in days.

Check contract and lease dates

Verify expiry dates, notice periods, and payment terms by calculating the exact number of days between signing and deadline.

Plan milestones and timelines

Find anniversary milestones (1000 days, 10,000 days), project durations, or probation period end dates.

How Many Days Until My Birthday / Event?

To find how many days until an upcoming event, use the Date Difference tab. Set the start date to today and the end date to your event. The "days" hero shows the exact count. The year/month/day breakdown helps if you need to say "3 months and 12 days" rather than a raw number.

For recurring events like birthdays, the Age Calculator tab automatically shows "days until next birthday" so you don't need to switch tabs.

Age in Days — Why It Matters

Knowing your age in days is more than a curiosity. It's used in medical records, scientific research, legal contexts (calculating age for pension eligibility), and project timelines.

A person born on January 1, 1990 turned 10,000 days old on May 19, 2017. On their 18th birthday they were 6,570 days old. Retirement at 65 is 23,725 days from birth.

The Age Calculator shows total days, total weeks, and approximate hours so you have every unit available without needing to convert manually.

Frequently Asked Questions

Use the Date Difference tab. Enter a start date and end date, and the calculator instantly shows the total days, along with the breakdown in years, months, days, weeks, and total hours. The order doesn't matter — it always shows the absolute difference.

Use the Age Calculator tab. Enter your date of birth and the tool calculates your age as of today in years, months, and days — plus your total age in days, weeks, and hours. It also shows what day of the week you were born on, your zodiac sign, and how many days until your next birthday.

Use the Add / Subtract tab. Set the start date to today (default), then click the "+30 days", "+60 days", or "+90 days" quick preset buttons, or enter any number of days. The result date is shown with the day of the week.

Go to the Age Calculator tab, enter your birthdate, and the "total days" metric shows exactly how many days you have been alive. For example, someone born on January 1, 1990 is approximately 12,900+ days old as of 2025.

Use the Date Difference tab. Set today as the start date and your event date as the end date. The "days" metric shows the total number of days remaining. Alternatively, use the Add/Subtract tab to confirm by working backwards from the event.

Yes. In the Add / Subtract tab, enter a negative number in the days field (or use the quick preset buttons like "−30 days", "−1 week", "Yesterday"). The result shows the date that many days before your start date.

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