<P> Schools and universities in Australia typically have academic years that roughly align with the calendar year (i.e., starting in February or March and ending in October to December), as the southern hemisphere experiences summer from December to February . </P> <P> In the International System of Quantities, the year (symbol, a) is defined as either 365 days or 366 days . </P> <P> The Julian year, as used in astronomy and other sciences, is a time unit defined as exactly 365.25 days . This is the normal meaning of the unit "year" (symbol "a" from the Latin annus) used in various scientific contexts . The Julian century of 7004365250000000000 ♠ 36 525 days and the Julian millennium of 7005365250000000000 ♠ 365 250 days are used in astronomical calculations . Fundamentally, expressing a time interval in Julian years is a way to precisely specify how many days (not how many "real" years), for long time intervals where stating the number of days would be unwieldy and unintuitive . By convention, the Julian year is used in the computation of the distance covered by a light - year . </P> <P> In the Unified Code for Units of Measure, the symbol, a (without subscript), always refers to the Julian year, a, of exactly 7007315576000000000 ♠ 31 557 600 seconds . </P>

According to science how many days are in a year