Tropical Years to Hours (yr (trop) to h)
1 tropical year equals 8,765.81256 hours exactly.
How to convert tropical years to hours
To convert tropical years to hours, multiply the number of tropical years by 8,765.81256. This factor is exact. To go the other way, multiply hours by 0.0001140795554 (rounded).
hours = tropical years × 8,765.81256
Example: 10 tropical years = 87,658.1256 hours.
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 tropical 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
Tropical Year (yr (trop))
About 365.24219 days, the time between successive spring equinoxes. The Gregorian calendar approximates it.
Tropical comes from a Greek word meaning turning, and this year is measured by the cycle of the seasons: the time for the Sun to return to the same ecliptic longitude. The mean value at the start of 2000 was 365.2421897 days, or 365 days 5 hours 48 minutes 45.19 seconds. Individual intervals between March equinoxes wander by minutes, so the mean is what is normally quoted.
Hipparchus timed equinoxes in the second century BC and arrived at 365 days 5 hours 55 minutes 12 seconds, a little long. The Alfonsine Tables of 1252 gave 365 days 5 hours 49 minutes 16 seconds, and this value guided the Gregorian reform of 1582, which was needed because the equinox had slipped about ten days from its date at the Council of Nicaea in 325.
Kepler's Rudolphine Tables of 1627 came within a second or so of the modern figure, and Simon Newcomb's 1898 value of about 365.24219878 days served the national almanacs until 1983. The Gregorian calendar averages 365.2425 days, which tracks the tropical year closely.
1 tropical year = 31,556,925.22 seconds (approximately).
Sources: Wikipedia: Tropical year; NASA Earth Fact Sheet
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
Related conversions
- Hours to tropical years (reverse)
- Tropical years to seconds
- Tropical years to minutes
- Tropical years to days
- Tropical years to weeks
- Tropical years to months
- Tropical years to years
- Seconds to hours
- Minutes to hours
- Days to hours
- Weeks to hours
- Months to hours
- Years to hours
- Milliseconds to hours
- Microseconds to hours
- Nanoseconds to hours
- Decades to hours
- Centuries to hours
- Millennia to hours
See all time units.