Date & Age Calculator
Count the days between two dates, or find an age from a birthdate. It runs entirely in your browser, so the file never leaves your computer.
Counting days is harder than it looks
Months are different lengths, February changes, and counting on your fingers across a year boundary goes wrong somewhere in the middle. It is the sort of arithmetic that feels like it should be easy and reliably is not.
Two modes: days between any two dates, with a weeks-and-days breakdown, and age in completed years plus months and days from a date of birth.
Leap years, properly
Both modes use real calendar dates rather than approximating a year as 365 days, so leap days are counted where they fall.
The effect is small and real: 28 February to 1 March is two days in 2024 and one day in 2025. Anything that averages the year instead of reading the calendar will drift, and over a long span it drifts noticeably.
Age on a date other than today
The age mode defaults to today but takes any "age on" date. That covers the cases people actually need it for — how old someone will be at a wedding, age on a cutoff date for a form, age at the time of a past event.
Everything is calculated in your browser, which matters more than it sounds for a tool whose input is somebody's date of birth.
Questions
Common questions
What does this tool do?
Two things: it counts the number of days between any two dates, and it works out an age in years (with months and days) from a date of birth.
How do I count days between two dates?
Use the 'Days between dates' mode and pick a start and end date. It shows the total number of days, plus a breakdown in weeks and days.
How do I calculate an age?
Use the 'Age from birthdate' mode, enter the date of birth, and optionally change the 'age on' date (it defaults to today). It shows completed years, plus the months and days.
Does it handle leap years?
Yes. Both the day count and the age calculation use real calendar dates, so leap years (like the extra day in February 2024) are counted correctly.
What if the end date is before the start date?
For days between, it shows the gap and notes that the end date is earlier. For age, the date must be on or after the birthdate, or it asks you to fix it.
Is anything uploaded?
No. All the date math happens in your browser — no ads, nothing sent anywhere.
Our own software
Dictate it instead of typing it
Hold a key, say the sentence, and the words land in whatever Windows window you were already in. Runs on your own PC — no account, no upload, nothing to renew.
$79 launch price · $99 regular · buy once