In astronomy, the Julian year is a unit of time; it is defined as 365.25 days of exactly 86400 seconds (SI base unit), totalling exactly 31557600 seconds in the Julian astronomical year.
The word "year" is also used for periods loosely associated with, but not identical to, the calendar or astronomical year, such as the seasonal year, the fiscal year, the academic year, etc. Similarly, "year" can mean the orbital period of any planet: for example, a Martian year or a Venusian year are examples of the time a planet takes to transit one complete orbit. The term can also be used in reference to any long period or cycle, such as the Great Year.[