Date+Quarters.swift

extension Date {
    var quarter: Int {
        let month = Calendar.current.dateComponents([.month], from: self).month!
        return month / 3 + 1
    }

    var beginningOfQuarter: Date {
        var calendar = Calendar.current
        calendar.timeZone = .current
        let inComps = calendar.dateComponents([.year, .month], from: self)
        let year = inComps.year!
        let month = 3 * ((inComps.month! - 1) / 3) + 1
        let components = DateComponents(year: year, month: month, day: 1, hour: 0, minute: 0, second: 0)
        return calendar.date(from: components)!
    }
    
    var endOfQuarter: Date {
        var calendar = Calendar.current
        calendar.timeZone = .current
        let inComps = calendar.dateComponents([.year, .month], from: self)
        let quarter = self.quarter
        let year = inComps.year! + 3 * quarter / 12
        let month = 3 * quarter % 12 + 1
        let components = DateComponents(year: year, month: month, day: 1, hour: 0, minute: 0, second: 0)
        let date = calendar.date(from: components)!
        return calendar.date(byAdding: DateComponents(second: -1), to: date)!
    }
}