How to Convert Time Units
Enter the value you want to convert in the Value field.
Select the source unit in the From list.
Select the target unit in the To list.
The result appears instantly below the unit selectors.
Key Features
33 Time Units
Covers everything from Planck time and attoseconds to millennia and quindecennials.
Precise Conversions
Uses exact multipliers for each unit, with automatic formatting that avoids unnecessary scientific notation for everyday values.
Astronomical & Sidereal Units
Includes Julian year, tropical year, sidereal year, sidereal day, synodic month, and more for scientific use.
Works Offline
All conversions run entirely in your browser. No internet connection is needed after the page loads.
Privacy-First
No data is ever sent to a server. Your values stay on your device.
Privacy & Security
All time conversions are calculated entirely in your browser using JavaScript. No input is uploaded or transmitted anywhere.
Frequently Asked Questions
What is the difference between a Julian year and a tropical year?
A Julian year is exactly 365.25 days (31,557,600 seconds), defined for use in astronomy. A tropical year (31,556,925 seconds) is the time it takes Earth to complete one full orbit relative to the Sun, and is the basis for the Gregorian calendar.
What is a sidereal day?
A sidereal day (86,164.09 seconds) is the time it takes Earth to rotate 360° relative to distant stars — about 4 minutes shorter than a solar day (86,400 seconds).
What is Planck time?
Planck time (~5.39 × 10⁻⁴⁴ seconds) is the smallest meaningful unit of time in physics — the time it takes light to travel one Planck length in a vacuum.
What is a shake?
A shake is an informal unit equal to 10 nanoseconds (1 × 10⁻⁸ seconds), used in nuclear physics to describe time intervals in chain reactions.
How is a month calculated here?
The generic month uses the average Gregorian month (2,629,800 seconds, or 1/12 of a Julian year). The synodic month (2,551,442.8 seconds) is the average time between two full moons.