How Long Is a Tropical Year / Solar Year?
The length of a tropical year is the time it takes for the seasons to repeat—roughly the time it takes the Earth to complete an orbit around the Sun.
A tropical, common, and leap year.
A Year Is Never 365 Days Long
A tropical year, also known as a solar year, an astronomical year, or an equinoctial year, is, on average, approximately 365 days, 5 hours, 48 minutes and 45 seconds long (365.24219 days).
A tropical year can be measured from either the vernal or autumnal equinox to the next one, or from the Summer or the winter solstice to the next one.
On timeanddate.com, we calculate a tropical year from the March equinox to the next March equinox (see table below).
What are equinoxes and solstices?
Leap Day Synchronizes Calendar
Although a common year has 365 days in today's Gregorian calendar, we add a leap day nearly every four years to stay in sync with the tropical year.
Without the correct amount of leap years, our calendar would quickly become out of sync. This happened to the Julian calendar, which had too many leap years. Eventually, it was replaced with the Gregorian calendar.
Can Vary by 30 Minutes
The exact length of a tropical year can vary by up to around half an hour. For instance, the tropical year 2032 will last longer than 365 days and 6 hours. 2027, however, will only last 365 days, 5 hours, and 39 minutes.
List of all tropical years 1900–2100
Length of Tropical Year 2010–2030
Tropical year measured from/to the March equinox. Accuracy believed to be within a few seconds. Leap seconds are accounted for.
| Days | Hours | Minutes | Seconds | |
|---|---|---|---|---|
| 三月 2010 – 三月 2011 | 365 | 5 | 48 | 23 |
| 三月 2011 – 三月 2012 | 365 | 5 | 53 | 56 |
| 三月 2012 – 三月 2013 | 365 | 5 | 47 | 22 |
| 三月 2013 – 三月 2014 | 365 | 5 | 55 | 14 |
| 三月 2014 – 三月 2015 | 365 | 5 | 48 | 2 |
| 三月 2015 – 三月 2016 | 365 | 5 | 44 | 56 |
| 三月 2016 – 三月 2017 | 365 | 5 | 58 | 36 |
| 三月 2017 – 三月 2018 | 365 | 5 | 46 | 41 |
| 三月 2018 – 三月 2019 | 365 | 5 | 43 | 12 |
| 三月 2019 – 三月 2020 | 365 | 5 | 51 | 4 |
| 三月 2020 – 三月 2021 | 365 | 5 | 47 | 55 |
| 三月 2021 – 三月 2022 | 365 | 5 | 55 | 54 |
| 三月 2022 – 三月 2023 | 365 | 5 | 50 | 55 |
| 三月 2023 – 三月 2024 | 365 | 5 | 42 | 8 |
| 三月 2024 – 三月 2025 | 365 | 5 | 54 | 53 |
| 三月 2025 – 三月 2026 | 365 | 5 | 44 | 39 |
| 三月 2026 – 三月 2027 | 365 | 5 | 38 | 39 |
| 三月 2027 – 三月 2028 | 365 | 5 | 52 | 27 |
| 三月 2028 – 三月 2029 | 365 | 5 | 44 | 57 |
| 三月 2029 – 三月 2030 | 365 | 5 | 49 | 56 |
Tropical years from 1900 to 2100
Tropical Year versus Sidereal Year
A tropical year is roughly—but not exactly—the time it takes the Earth to complete one orbit around the Sun.
Because the orientation of Earth’s tilt has a slight wobble (a motion called precession), the time from one March equinox to the next is a fraction shorter than Earth’s orbital period around the Sun.
The time for one orbital revolution around the Sun is called a sidereal year—this is approximately 365.25636 days.