About Us
DateTimeCalculatorPro is a free suite of date and time calculators that runs entirely in your browser. No accounts, no uploads, no tracking of what you calculate.
Why we built this
Date math looks simple until you actually do it. Month lengths vary from 28 to 31 days, leap years follow a rule most people get slightly wrong (divisible by 4 — except century years, which must be divisible by 400), and counting hours across midnight trips up even careful manual work. Existing tools often wrap this math in sign-ups, ads everywhere, or cloud uploads of information that should stay private.
We wanted the opposite: calculators that are precise, instant, and keep your data on your own device. Every calculation on this site — date differences, duration offsets, exact age — is executed by JavaScript running locally in your browser. Nothing you type or compute is sent to a server, logged, or stored anywhere.
What we offer
Date & Time Difference Calculator
The exact span between two dates or datetimes in years, months, weeks, days, hours, and minutes — with business-day breakdowns and leap-year handling.
Add / Subtract Date & Time
Offset any date by years, months, weeks, days, hours, or minutes, with month-end boundary clamping so results stay calendar-correct.
Exact Age Calculator
Age in years, months, and days from any birth date — including future target dates, birthday countdowns, and February 29 handling.
Our principles
- ✓Privacy by default. 100% client-side computation. Your dates and times never leave your device.
- ✓Accuracy over shortcuts. True Gregorian calendar arithmetic, not approximations.
- ✓Free and frictionless. No accounts, no paywalls, no data in exchange for answers.
- ✓Accessible and fast. Works on mobile and desktop, with keyboard and screen-reader friendly controls.
Get in touch
Found a bug, spotted an inaccuracy, or want a feature? We read everything. Reach us at [email protected] or through the contact page.