Time Converter
Time Converter — Convert Seconds, Minutes, Hours, Days & More
Our free online Time Converter lets you instantly convert between 32+ units of time — from everyday units like seconds, minutes, hours, and days to scientific units like nanoseconds, femtoseconds, and Planck time, plus historical periods like decades, centuries, and millennia. Whether you need to convert hours to seconds, days to minutes, years to hours, or microseconds to milliseconds, this tool delivers instant and accurate results.
Time is a fundamental physical quantity that orders the sequence of events. It is measured in many units depending on the scale:
- Standard SI: second (s), millisecond (ms), microsecond (µs), nanosecond (ns)
- Everyday: minute (min), hour (h), day (d), week, month, year
- Long periods: decade, century, millennium
- Astronomical: sidereal day, sidereal year, Julian year, tropical year
- Scientific extremes: femtosecond (fs), attosecond (as), Planck time
All conversions use standardized definitions and high-precision arithmetic, making this tool reliable for science, computing, scheduling, astronomy, and everyday calculations.
Common Time Conversion Reference
Here are the most frequently used time conversions for quick reference:
- 1 minute = 60 seconds
- 1 hour = 60 minutes = 3,600 seconds
- 1 day = 24 hours = 1,440 minutes = 86,400 seconds
- 1 week = 7 days = 168 hours = 604,800 seconds
- 1 year (Julian) = 365.25 days = 8,766 hours = 31,557,600 seconds
- 1 decade = 10 years = 315,576,000 seconds
- 1 century = 100 years = 3,155,760,000 seconds
- 1 millisecond = 0.001 seconds; 1 microsecond = 0.000001 seconds
Frequently Asked Questions — Time Converter
Question: How do I use the Time Converter?
Answer: Select the unit you are converting from in the left list and the unit to convert to in the right list, then type your value. The result appears instantly across all listed units.
Question: How many seconds are in an hour?
Answer: There are exactly 3,600 seconds in one hour (60 minutes × 60 seconds = 3,600 seconds).
Question: How many seconds are in a day?
Answer: There are exactly 86,400 seconds in one day (24 hours × 60 minutes × 60 seconds = 86,400 seconds).
Question: How many days are in a year?
Answer: A common year has 365 days; a leap year has 366 days. The Julian year is defined as exactly 365.25 days (31,557,600 seconds). The tropical (solar) year is approximately 365.2422 days.
Question: What is a millisecond?
Answer: A millisecond (ms) is one-thousandth of a second (0.001 s). Human reaction time is typically 150–300 milliseconds. Computer processors operate in nanoseconds or faster.
Question: What is a nanosecond?
Answer: A nanosecond (ns) is one billionth of a second (10⁻⁹ s). Light travels about 30 centimeters (roughly one foot) in a nanosecond. Computer clock speeds are measured in gigahertz (GHz), where each cycle takes about 1 nanosecond.
Question: What is the difference between a sidereal day and a solar day?
Answer: A solar day is 24 hours — the time for the Sun to return to the same position in the sky. A sidereal day is about 23 hours, 56 minutes, and 4 seconds — the time for Earth to rotate 360° relative to distant stars. The difference is because Earth also moves along its orbit while rotating.
Question: What is a fortnight?
Answer: A fortnight is a period of 14 days (two weeks) or 1,209,600 seconds. The word comes from "fourteen nights" and is commonly used in British English for scheduling and payment periods.
Question: What is Planck time?
Answer: Planck time is the smallest meaningful unit of time in physics, approximately 5.391 × 10⁻⁴⁴ seconds. It represents the time for light to travel one Planck length. At scales smaller than Planck time, current physics cannot describe events meaningfully.
Question: How accurate are the time conversions in this tool?
Answer: All conversions use standardized definitions with up to 12 significant digits of precision, suitable for scientific, engineering, scheduling, astronomical, and everyday time calculations.