About Time & Duration

Time & Duration is an independent engineering project and high-precision time calculations initiative. Founded to deliver zero-bloat, mathematically exact duration tools to users worldwide without requiring complex logins or paywalls.

Our Core Principles

Absolute Accuracy: Every converter is peer-reviewed against global ISO and NIST metrics.
Privacy First: No tracking scripts, cookie payloads, or database logs.
Open Access: 100% free forever for students, developers, and payroll managers alike.

Time & Duration Calculator Suite

Fast, accurate tools for anything involving time — elapsed hours, date math, work shifts, and time zones. Pick a calculator below and get your answer in seconds.

Time Calculators

Time Duration Calculator — Find out exactly how many hours, minutes, and seconds sit between two clock times. Works with AM/PM or 24-hour time.
Time Addition & Subtraction Calculator — Sum or subtract cumulative lists of hours, minutes, and seconds with sexagesimal carryovers.
Time Difference Calculator — Compare two times or timestamps and get the gap down to the minute.
Working Hours Calculator — Total up paid hours for a shift, including unpaid breaks — useful for timesheets and payroll.
Overnight Shift Calculator — Built specifically for shifts that cross midnight, where a normal calculator gets the math wrong.
FLSA 7-Minute Rule Calculator — DOL 29 CFR § 785.48(b) compliant 15-minute time clock rounding calculator.
Countdown Timer — Set a countdown to any date and time, live-updating.
Stopwatch / Timer — Simple, ad-light stopwatch and countdown timer tools you can run right in the browser.

Date Calculators

Date Duration Calculator — Get the full gap between two dates in years, months, weeks, and days — useful for contracts, anniversaries, or project timelines.
Date Add/Subtract Calculator — Add or subtract days, weeks, months, or years from any date. Handy for deadlines, due dates, and expiry calculations.
Age Calculator — Enter a birth date and get an exact age in years, months, and days (down to the hour, if you want it).
Business Days Calculator — Count working days between two dates, automatically skipping weekends and holidays.
Leap Year Calculator — Check whether any given year is a leap year, and see the next one coming up.

Time Zone & Format Tools

Guides & How-Tos

Not sure which calculation you need, or want to understand the math behind it? These guides walk through the formulas step by step.

How to Calculate Time Duration Between Two Times
The Complete Guide to Time & Date Calculations
Converting Seconds to Minutes (and Back)
Browse Complete Calculator Suite Directory
See all guides →