Traditionally, there are 52 weeks in a calendar year, which begins on January 1 and ends on December 31. There are 365 days in the internationally accepted Gregorian calendar, with the exception of a leap year occurring every four years, adding one extra day to the calendar year.
The Gregorian calendar, or Western calendar, is an astronomy-based calendar using the rotations of the Earth, Sun, and Moon. It is divided into 12 months, 52 weeks, and 365 days. Each month consists of either 30 or 31 days, except for February which consists of 28 days. In a leap year, an additional day is added on February 29.