In temperate and subpolar regions around the planet, four seasons are generally recognized: spring, summer, autumn and winter.
In tropical and subtropical regions several geographical sectors do not present defined seasons; but in the seasonal tropics, the annual wet and dry seasons are recognized and tracked. A calendar year is an approximation of the number of days of the Earth's orbital period as counted in a given calendar.
As 218 out of every 900 years are leap years, the average (mean) length of this Julian year is A calendar era assigns a cardinal number to each sequential year, using a reference point in the past as the beginning of the era.
The Gregorian, or modern, calendar, presents its calendar year to be either a common year of 365 days or a leap year of 366 days, as do the Julian calendars; see below.
For the Gregorian calendar the average length of the calendar year (the mean year) across the complete leap cycle of 400 years is 365.2425 days.
Examples include Chinese 年 "year", originally 秂, an ideographic compound of a person carrying a bundle of wheat denoting "harvest".
Slavic besides godŭ "time period; year" uses lěto "summer; year".
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.