Hours to Sidereal Years (h to yr (sid))
1 hour equals 0.0001140751288 sidereal years (rounded).
How to convert hours to sidereal years
To convert hours to sidereal years, multiply the number of hours by 0.0001140751288. The factor is rounded to 10 significant digits. To go the other way, multiply sidereal years by 8,766.152712.
sidereal years = hours × 0.0001140751288
Example: 10 hours = 0.001140751288 sidereal years.
Months and years are not constant. This site uses the average Gregorian year of 365.2425 days, so one 'year' converts to 365.2425 days, not 365; use 'common year' for exactly 365 days.
Approximate value. Standards for the sidereal year varied by place and period, so this converter uses the most commonly cited value. Treat results as estimates, not exact figures.
About these units
Hour (h)
60 minutes or 3,600 seconds, one twenty-fourth of a mean solar day.
Egyptian astronomers gave us the twelve. Coffin lids from about 2150 BC show the night divided into exactly 12 intervals, tied to the rising of star groups called decans, and the day was later split into 12 hours with sundials. These were seasonal hours, a twelfth of the daylight, so a summer hour was longer than a winter one. The word itself comes from Greek hora, originally any span of time, through Latin and Old French into English in the 13th century.
Equal hours of 1/24 of a day were probably first proposed by Hipparchus, and mechanical clocks made them the practical choice, since a clock showing seasonal hours had to be readjusted every morning and evening. Today the hour is exactly 3,600 seconds and is a non-SI unit accepted for use with the SI. Civil time still bends it a little: UTC hours have lasted 3,601 seconds 27 times since 1972 to keep clocks within 0.9 seconds of the Earth's rotation. In practice we use it for working shifts, travel times and electricity bills measured in kilowatt-hours.
1 hour = 3,600 seconds (exactly).
Sources: Wikipedia: Hour; BIPM: SI Brochure, 9th edition
Sidereal Year (yr (sid))
About 365.256363 days, the time for Earth to return to the same position relative to the fixed stars.
Measured against the fixed stars, one orbit of Earth around the Sun takes about 365.256363 days, or roughly 365 days 6 hours 9 minutes 10 seconds. That is the sidereal year, and it is about 20 minutes 25 seconds longer than the mean tropical year used for the seasons.
The gap exists because of the precession of the equinoxes, which Hipparchus identified in 127 BC after comparing the two kinds of year. Ptolemy later reported his sidereal figure as about 365 days 6 hours 10 minutes, already close to the modern value. Earlier peoples had tracked the year by star events instead, such as the Egyptian watch for the rising of Sirius before the Nile flood, and Hesiod's farming advice tied to the Pleiades.
Indian astronomy kept the sidereal year in its calendars. The Surya Siddhanta gave a value near 365 days 6 hours 12 minutes 36.56 seconds, slightly long by modern measurement. NASA's fact sheet lists the sidereal orbital period of Earth as 365.256 days.
1 sidereal year = 31,558,149.76 seconds (approximately).
Sources: Wikipedia: Sidereal year; NASA Earth Fact Sheet
Related conversions
- Sidereal years to hours (reverse)
- Hours to seconds
- Hours to minutes
- Hours to days
- Hours to weeks
- Hours to months
- Hours to years
- Hours to milliseconds
- Hours to microseconds
- Hours to nanoseconds
- Hours to decades
- Hours to centuries
- Hours to millennia
- Seconds to sidereal years
- Minutes to sidereal years
- Days to sidereal years
- Weeks to sidereal years
- Months to sidereal years
- Years to sidereal years
See all time units.