Number of days in given year using iPhone SDK?

Question

I'm trying to get the number of days in a current year.

When I try the solution on Number of days in the current month using iPhone SDK?, and replace NSMonthCalendarUnit by NSYearCalendarUnit, I still get the number of days for that month.

Does anyone know how I should do this?

Thanks in advance for your help.

Answer 1

Here's a super accurate NSCalendar extension in Swift 2:

extension NSCalendar {
    func daysInYear(date: NSDate = NSDate()) -> Int? {
        let year = components([NSCalendarUnit.Year], fromDate: date).year
        return daysInYear(year)
    }

    func daysInYear(year: Int) -> Int? {
        guard let begin = lastDayOfYear(year - 1), end = lastDayOfYear(year) else { return nil }
        return components([NSCalendarUnit.Day], fromDate: begin, toDate: end, options: []).day
    }

    func lastDayOfYear(year: Int) -> NSDate? {
        let components = NSDateComponents()
        components.year = year
        guard let years = dateFromComponents(components) else { return nil }

        components.month = rangeOfUnit(NSCalendarUnit.Month, inUnit: NSCalendarUnit.Year, forDate: years).length
        guard let months = dateFromComponents(components) else { return nil }

        components.day = rangeOfUnit(NSCalendarUnit.Day, inUnit: NSCalendarUnit.Month, forDate: months).length

        return dateFromComponents(components)
    }
}

You can use it like this:

let calendar = NSCalendar.currentCalendar() // I'm using the Gregorian calendar
calendar.daysInYear()     // 365 (since it's currently 2015)
calendar.daysInYear(2016) // 366 (leap year!)

This is super flexible since we don't assume anything about the length of the calendar:

let hebrew = NSCalendar(calendarIdentifier: NSCalendarIdentifierHebrew)
hebrew?.daysInYear(-7)   // 354
hebrew?.daysInYear(-100) // 384

Enjoy.

Answer 2

If you're only going to use the Gregorian Calender, you can calculate it manually.

http://en.wikipedia.org/wiki/Leap_year#Algorithm

if year modulo 400 is 0 then leap
 else if year modulo 100 is 0 then no_leap
 else if year modulo 4 is 0 then leap
 else no_leap