Date & Age Calculator
Calculate days between dates, add or subtract days, and get the calendar week and day of the week, helpful for scheduling and date planning. GDPR-compliant.
Your inputs are processed in your browser and are not transmitted to our servers. Note: third-party resources (e.g. advertising and analytics from Google/Cloudflare) and an optional PayPal donation link may transfer data when loading or when clicked. Browser extensions or plugins may be able to read content that is visible in the input fields.
The result will appear here …
How to use this tool (video)
This video is hosted on YouTube. When you play it, data may be sent to Google.
Date Calculator: Days Between Dates, Age, and More
Find the number of days between two dates, add or subtract days, or calculate an exact age. The date calculator also shows weekdays, calendar weeks, months, years, and leap-year details. It runs 100 % in your browser and uses your device's system clock.
Three practical date calculations
The tool offers three modes that all work with real calendar dates:
- Days between dates: the difference of two dates in days, broken down into weeks, months and years.
- Add or subtract days: a date moved forward or backward by a chosen number of days.
- Age calculator: from a date of birth up to a reference date (or today if none is given).
An important detail: calendar months have different lengths, between 28 and 31 days. The calculator therefore always works on real dates and treats leap years, including 29 February, correctly.
Worked examples with real numbers:
- Between 15 January 2026 and 15 February 2026 there are 31 days (January has 31 days).
- 1 March 2026 plus 90 days gives 30 May 2026.
- February 2026 has 28 days; 1 February plus 28 days gives 1 March.
When is the date calculator useful?
- Project planning: the duration between milestones or setting deadlines
- Age calculation: the exact age in years, months and days
- Legal and contractual deadlines: a date offset by a fixed number of days
- Holiday planning: how many days between the start and end of a trip
- Calendar week: the current or a future week number
What it can and cannot do
The calculator gives exact calendar days but does not take public holidays, working-day rules or statutory deadline calculations into account. For binding legal or contractual deadlines, check the relevant rules. Because the tool uses the time and time zone of your own device and runs locally, all figures match your current system settings; there is no server-based clock. Also note that month and year figures can appear rounded, since month lengths vary depending on where the dates fall.
Frequently asked questions
How do I calculate the number of days between two dates?
Choose the days between dates mode and enter a start and end date. The result shows the difference in days, weeks, months and years, plus the weekday of both dates.
How do I add or subtract days from a date?
In the add or subtract days mode, enter a start date and the number of days you want to add or subtract. Use a negative value to move into the past.
Why do months have different lengths?
Calendar months have 28 to 31 days, and February has 28 or 29 depending on the year. The calculator works on real calendar dates instead of assuming a fixed month length, so the results are correct.
How do I calculate my exact age?
Choose the age calculator and enter your date of birth plus an optional reference date. Without a reference date, the calculator counts until today and shows your age in years, months, days and total days.
What does the calendar week tell me?
The calendar week numbers the weeks of a year from 1 to 52 or 53. In the add or subtract days mode, the calculator shows the calendar week of the resulting date automatically.
Are leap years taken into account?
Yes. The calculator detects leap years automatically and handles 29 February correctly, so month and day values stay accurate across irregular year lengths.
Are my data stored?
No. All calculations run directly in your browser using your device time. Your inputs are not sent to a server, stored or shared.