Instance Property

yearForWeekOfYear

iOS 8.0+ iPadOS 8.0+ Mac Catalyst 8.0+ macOS 10.9+ tvOS 9.0+ watchOS 2.0+

The year corresponding to a week-counting week.

var yearForWeekOfYear: Int? { get set }

Discussion

The Gregorian calendar defines a week to have 7 days, and a year to have 365 days, or 366 in a leap year. However, neither 365 or 366 divide evenly into a 7 day week, so it is often the case that the last week of a year ends on a day in the next year, and the first week of a year begins in the preceding year. To reconcile this, ISO 8601 defines a week-numbering year, consisting of either 52 or 53 full weeks (364 or 371 days), such that the first week of a year is designated to be the week containing the first Thursday of the year.

You can use the yearForWeekOfYear property with the weekOfYear and weekday properties to get the date corresponding to a particular weekday of a given week of a year. For example, the 6th day of the 53rd week of the year 2005 (ISO 2005-W53-6) corresponds to Sat 1 January 2005 on the Gregorian calendar.

Note

This value is interpreted in the context of the calendar in which it is used.