About Date & Time Utilities
Date & Time Utilities is a free collection of online tools for working with dates and times. Whether you need to calculate the days between two dates, convert time units, count down to a holiday, or figure out your exact age, our tools are designed to give you instant, accurate results with as little input as possible.
All calculations run entirely in your browser — no data is sent to any server, no accounts are needed, and there's nothing to install. Just pick a tool, enter your dates or numbers, and get your answer.
What we offer
- Holiday countdowns — see how many days remain until Christmas, Thanksgiving, Diwali, Halloween, and dozens more
- Date difference calculators — find the gap between any two dates in seconds, minutes, hours, days, business days, weeks, months, or years
- Time unit converters — convert between seconds, minutes, hours, days, weeks, months, and years with full precision
- Age calculator — enter your birthdate and see your exact age broken down into years, months, and days
- Countdown to any date — pick a target date and see how many days are left
Why use Date & Time Utilities?
- Privacy first — no tracking, no cookies, no data collection. Everything happens in your browser.
- No sign-up — all tools are free and available immediately, no account required.
- Accurate math — years use 365.25 days (accounting for leap years), business day calculations skip weekends, and all results show full precision.
- Works everywhere — every tool is responsive and works on phones, tablets, and desktops.
- Fast and lightweight — no heavy JavaScript frameworks. Pages load instantly and calculations are immediate.
How our calculators work
Each calculator uses JavaScript's built-in Date object for reliable date math. Dates are normalized to midnight to avoid timezone and daylight saving time issues. Time unit conversions use a seconds-based approach: every value is first converted to seconds, then divided by the target unit's factor. This ensures consistent, accurate results across all unit pairs.
Who makes this
Date & Time Utilities is built and maintained by Shinji Furuya, a Senior Frontend Engineer with a decade of production React and TypeScript experience. It started as a personal answer to a simple frustration: most date calculators are buried in ads, get leap years and time zones subtly wrong, or make you sign up. This site is the opposite — accurate math, no accounts, and results that run entirely in your browser. If you spot a bug or a calculation that looks off, let me know — correctness is the whole point.
Sources & standards
The conventions used across the site follow widely accepted standards. The average year of 365.25 days is the Julian year used in astronomy; leap years follow the Gregorian calendar leap-year rule; and the second is defined by the SI standard. Business-day counts follow the Monday–Friday workweek and exclude weekends only, since public holidays vary by country and employer.