Tropical Years to Days (yr (trop) to d)
1 tropical year equals 365.24219 days exactly.
How to convert tropical years to days
To convert tropical years to days, multiply the number of tropical years by 365.24219. This factor is exact. To go the other way, multiply days by 0.002737909331 (rounded).
days = tropical years × 365.24219
Example: 10 tropical years = 3,652.4219 days.
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
Day (d)
24 hours or 86,400 seconds. The mean solar day; the actual rotation of the Earth is about 4 minutes shorter (see sidereal day).
Old English dæg is the root of our day, with close cousins in German Tag, Dutch dag and Icelandic dagur, all descending from Proto-Germanic dagaz. It is the oldest unit here, because the cycle of light and dark needs no instrument. Yet the day we count is a constructed average: the actual interval from one noon to the next varies through the year by up to about 7.9 seconds, because Earth's orbit is elliptical and its axis is tilted.
Astronomers smooth this out with a fictitious mean Sun, giving the mean solar day, and the day in the SI sense is fixed at exactly 86,400 seconds. Reality has drifted slightly: the mean solar day has recently averaged about 86,400.002 seconds, and tidal drag from the Moon is lengthening it by about 2 milliseconds per century. That is why 27 leap seconds were added to UTC between 1972 and 2022. One rotation measured against the distant stars is shorter, about 23 hours 56 minutes 4.09 seconds, and a year contains one more of these sidereal days than solar days.
1 day = 86,400 seconds (exactly).
Sources: Wikipedia: Day; BIPM: SI Brochure, 9th edition
Related conversions
- Days to tropical years (reverse)
- Tropical years to seconds
- Tropical years to minutes
- Tropical years to hours
- Tropical years to weeks
- Tropical years to months
- Tropical years to years
- Seconds to days
- Minutes to days
- Hours to days
- Weeks to days
- Months to days
- Years to days
- Milliseconds to days
- Microseconds to days
- Nanoseconds to days
- Decades to days
- Centuries to days
- Millennia to days
See all time units.