All calculators
Eleven date calculators, one directory
Choose the calculation that matches the dates you have. Each tool lists the inputs it needs and the result it returns, so you can open the right one without guessing.
Select a calculator
Each card names one calculation and its typical use. Open the tool that fits your dates.
Age Difference Calculator
Compare two dates of birth to see the gap between two people.
Birthday Countdown Calculator
See how many days remain until the next birthday or a chosen event date.
Date of Birth Calculator
Work backward from an age or a known date to estimate a date of birth.
How results are calculated
Every result is checked as you type
All eleven tools run in your browser. Inputs are validated before any calculation, and each result shows the unit and the dates it counted.
1. Validate the inputs
Each field must hold a real calendar date. Impossible dates and dates set in the wrong order are flagged before any result appears.
2. Count with calendar rules
Calculations follow the Gregorian calendar, including leap years, so month lengths and day counts stay consistent.
3. Show the working
Results list the unit used and the start and end dates, so you can check the figure against your own records.