Menu
Home
People
Places
Arts
History
Plants & Animals
Science
Life & Culture
Technology
Reference.org
Julian year (astronomy)
open-in-new
<p>In <a href="/facts/Astronomy/0ArJVM1p">astronomy</a>, a Julian year (symbol: a or aj) is a <a href="/facts/Units_of_measurement/pvTpWbmC">unit of measurement</a> of <a href="/facts/Time/HceJKUGB">time</a> defined as exactly 365.25 <a href="/facts/Day/MTAtWLDj">days</a> of 86400 <a href="/facts/SI/NShmfzlD">SI</a> <a href="/facts/Second/jtFxnJXx">seconds</a> each. The length of the Julian year is the average length of the <a href="/facts/Year/51V242hh">year</a> in the <a href="/facts/Julian_calendar/EQBtA1ML">Julian calendar</a> that was used in Western societies <a href="/facts/Adoption_of_the_Gregorian_calendar/zdTv43W5">until the adoption of the Gregorian Calendar</a>, and from which the unit is named. Nevertheless, because astronomical Julian years are measuring duration rather than designating dates, this Julian year does not correspond to years in the Julian calendar or any other calendar. Nor does it correspond to the many other ways of defining a year. </p>