A period between set dates that mark a year, from January 1 to December 31 by the Gregorian calendar, from Tishiri 1 to Elul 29 by the Jewish calendar, and from Muharram 1 to Dhu al-Hijjah 29 or 30 by the Islamic calendar.
A normal year has 365 full days, but there are 366 days in a leap year.