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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.

Illustration image
Illustration image

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).

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.

 DaysHoursMinutesSeconds
Maaliskuu 2010 – Maaliskuu 201136554823
Maaliskuu 2011 – Maaliskuu 201236555356
Maaliskuu 2012 – Maaliskuu 201336554722
Maaliskuu 2013 – Maaliskuu 201436555514
Maaliskuu 2014 – Maaliskuu 20153655482
Maaliskuu 2015 – Maaliskuu 201636554456
Maaliskuu 2016 – Maaliskuu 201736555836
Maaliskuu 2017 – Maaliskuu 201836554641
Maaliskuu 2018 – Maaliskuu 201936554312
Maaliskuu 2019 – Maaliskuu 20203655514
Maaliskuu 2020 – Maaliskuu 202136554755
Maaliskuu 2021 – Maaliskuu 202236555554
Maaliskuu 2022 – Maaliskuu 202336555055
Maaliskuu 2023 – Maaliskuu 20243655428
Maaliskuu 2024 – Maaliskuu 202536555453
Maaliskuu 2025 – Maaliskuu 202636554439
Maaliskuu 2026 – Maaliskuu 202736553839
Maaliskuu 2027 – Maaliskuu 202836555227
Maaliskuu 2028 – Maaliskuu 202936554457
Maaliskuu 2029 – Maaliskuu 203036554956

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.

Topics: Calendar, Leap Year, Astronomy, Seasons