Calculate age from birth date

update: Xcode 11 • Swift 5.1

You can use the Calendar method dateComponents to calculate how many years from a specific date to today:

extension Date {
    var age: Int { Calendar.current.dateComponents([.year], from: self, to: Date()).year! }
}

---

let dob = DateComponents(calendar: .current, year: 2000, month: 6, day: 30).date!
let age = dob.age // 19

Important:

The timezone must be set to create a UTC birth date otherwise there will be inconsistencies between timezones.

Swift 3

extension Date {

    //An integer representation of age from the date object (read-only).
    var age: Int {
        get {
            let now = Date()
            let calendar = Calendar.current

            let ageComponents = calendar.dateComponents([.year], from: self, to: now)
            let age = ageComponents.year!
            return age
        }
    }

    init(year: Int, month: Int, day: Int) {
        var dc = DateComponents()
        dc.year = year
        dc.month = month
        dc.day = day

        var calendar = Calendar(identifier: .gregorian)
        calendar.timeZone = TimeZone(secondsFromGMT: 0)!
        if let date = calendar.date(from: dc) {
            self.init(timeInterval: 0, since: date)
        } else {
            fatalError("Date component values were invalid.")
        }
    }

}

Usage:

let dob = Date(year: 1975, month: 1, day: 1)
let age = dob.age

print(age)