Start date/end date for biweekly payroll frequency - Swift

Question

I have to present time trackings summary for specific payroll frequency periods: monthly, weekly, biweekly. I did find a way to get start date and end date for current week or current month ex.

var startOfMonth: Date? {
    let components = Calendar.current.dateComponents([.year, .month], from: startOfDay)
    return Calendar.current.date(from: components)
}

var endOfMonth: Date? {
    guard let startOfTheMonth = startOfMonth else { return nil }
    var components = DateComponents()
    components.month = 1
    components.second = -1
    return Calendar.current.date(byAdding: components, to: startOfTheMonth)
}

But how can I get those dates for current biweekly period?

I assume that biweekly periods (it is 26 paychecks a year) are every two weeks since start of current year: ex. 1st biweek is 1-2 week of the 2020 year is 1.01.20-12.01.20; 24th biweek is 47-48 week is 16.11.20-29.11.20 and last 26th biweek is 51-53 week is 14.12.20-31.12.20.

EDIT:

Based on @Leo Dabus answer I managed to get startOfBiweek and endOfBiweek. Thank you!

var startOfBiweek: Date? {
    let biweekIntervals = biweekIntervalsInSameYear(using: .iso8601)
    return biweekIntervals.first(where: { $0.contains(self)})?.start
}

var endOfBiweek: Date? {
    let biweekIntervals = biweekIntervalsInSameYear(using: .iso8601)
    return biweekIntervals.first(where: { $0.contains(self)})?.end
}

Answer 1

I don't know if there is an easier way to accomplish what you want but this is what I came up with. First I get all days in the same year. Then I create an array with 26 subarrays and group dates for every 2 weeks. Then I create an array of date intervals using the first and last date of each subarray.

extension Calendar {
    static let iso8601 = Calendar(identifier: .iso8601)
}
extension Date {
    func dayAfter(using calendar: Calendar = .current) -> Date {
        calendar.date(byAdding: .day, value: 1, to: noon(using: calendar))!
    }
    func noon(using calendar: Calendar = .current) -> Date  {
        calendar.date(bySettingHour: 12, minute: 0, second: 0, of: self)!
    }
    func startOfNextDay(using calendar: Calendar = .current) -> Date {
        calendar.startOfDay(for: dayAfter(using: calendar))
    }
    func lastSecondOfDay(using calendar: Calendar = .current) -> Date {
        calendar.date(byAdding: DateComponents(second: -1), to: calendar.startOfDay(for: dayAfter(using: calendar)))!
    }
    func weekOfYear(using calendar: Calendar = .current) -> Int { calendar.component(.weekOfYear, from: self) }
    func year(using calendar: Calendar = .current) -> Int { calendar.component(.year, from: self) }
    func month(using calendar: Calendar = .current) -> Int { calendar.component(.month, from: self) }
    func allDaysInSameYear(using calendar: Calendar = .current) -> [Date] {
        calendar.range(of: .day, in: .year, for: self)!.map {
            DateComponents(calendar: calendar,year: year(using: calendar), day: $0).date!
        }
    }
    func biweeksInSameYear(using calendar: Calendar = .current) -> [[Date]] {
        allDaysInSameYear(using: calendar).reduce(into: .init(repeating: [], count: 26)) {
            let weekOfYear = $1.weekOfYear(using: calendar)-1
            let index = weekOfYear > 51 ? 25 : weekOfYear / 2
            $0[index].append($1)
        }
    }
    func biweekIntervalsInSameYear(using calendar: Calendar = .current) -> [DateInterval] {
        biweeksInSameYear(using: calendar).map {
            DateInterval(start: $0.first!, end: $0.last!.lastSecondOfDay(using: calendar))
        }
    }
}

---

let biweekIntervals = Date().biweekIntervalsInSameYear(using: .iso8601)
for interval in biweekIntervals {
    print(interval.start.description(with: .current), interval.end.description(with: .current), terminator: "\n")
} 

---

This will print:

Wednesday, 1 January 2020 00:00:00 Sunday, 12 January 2020 23:59:59
Monday, 13 January 2020 00:00:00 Sunday, 26 January 2020 23:59:59
Monday, 27 January 2020 00:00:00 Sunday, 9 February 2020 23:59:59
Monday, 10 February 2020 00:00:00 Sunday, 23 February 2020 23:59:59
Monday, 24 February 2020 00:00:00 Sunday, 8 March 2020 23:59:59
Monday, 9 March 2020 00:00:00 Sunday, 22 March 2020 23:59:59
Monday, 23 March 2020 00:00:00 Sunday, 5 April 2020 23:59:59
Monday, 6 April 2020 00:00:00 Sunday, 19 April 2020 23:59:59
Monday, 20 April 2020 00:00:00 Sunday, 3 May 2020 23:59:59
Monday, 4 May 2020 00:00:00 Sunday, 17 May 2020 23:59:59
Monday, 18 May 2020 00:00:00 Sunday, 31 May 2020 23:59:59
Monday, 1 June 2020 00:00:00 Sunday, 14 June 2020 23:59:59
Monday, 15 June 2020 00:00:00 Sunday, 28 June 2020 23:59:59
Monday, 29 June 2020 00:00:00 Sunday, 12 July 2020 23:59:59
Monday, 13 July 2020 00:00:00 Sunday, 26 July 2020 23:59:59
Monday, 27 July 2020 00:00:00 Sunday, 9 August 2020 23:59:59
Monday, 10 August 2020 00:00:00 Sunday, 23 August 2020 23:59:59
Monday, 24 August 2020 00:00:00 Sunday, 6 September 2020 23:59:59
Monday, 7 September 2020 00:00:00 Sunday, 20 September 2020 23:59:59
Monday, 21 September 2020 00:00:00 Sunday, 4 October 2020 23:59:59
Monday, 5 October 2020 00:00:00 Sunday, 18 October 2020 23:59:59
Monday, 19 October 2020 00:00:00 Sunday, 1 November 2020 23:59:59
Monday, 2 November 2020 00:00:00 Sunday, 15 November 2020 23:59:59
Monday, 16 November 2020 00:00:00 Sunday, 29 November 2020 23:59:59
Monday, 30 November 2020 00:00:00 Sunday, 13 December 2020 23:59:59
Monday, 14 December 2020 00:00:00 Thursday, 31 December 2020 23:59:59

---

---

Another approach, this one seems shorter but I recommend testing it further:

extension Calendar {
    static let iso8601 = Calendar(identifier: .iso8601)
}
extension Date {
    func startOfYear(using calendar: Calendar = .current) -> Date {
        calendar.dateComponents([.calendar,.year], from: self).date!
    }
    func endOfYear(using calendar: Calendar = .current) -> Date {
        startOfYear(using: calendar).adding(.init(year: 1, second: -1))!
    }
    func adding(_ components: DateComponents, wrappingComponents: Bool = false, using calendar: Calendar = .current) -> Date? {
        calendar.date(byAdding: components, to: self)
    }
    func yearForWeekOfYear(using calendar: Calendar = .current) -> Int { 
        calendar.component(.yearForWeekOfYear, from: self)
    }
    func biweekIntervalsInSameYear(using calendar: Calendar = .current) -> [DateInterval] {
        let date = DateComponents(calendar: .iso8601, weekOfYear: 1, yearForWeekOfYear: yearForWeekOfYear(using: .iso8601)).date!
        var intervals: [DateInterval] = [.init(start: startOfYear(using: .iso8601), end: date.adding( .init(second: -1, weekOfYear: 2), using: calendar)!)]
        var weekOfYear = 3
        while let start = Calendar.iso8601.nextDate(after: date, matching: DateComponents(weekOfYear: weekOfYear), matchingPolicy: .strict) {
            if intervals.count < 25 {
                intervals.append(.init(start: start, end: start.adding( .init(second: -1, weekOfYear: 2), using: calendar)!)) } else if intervals.count == 25 {
                    intervals.append(.init(start: start, end: start.endOfYear(using: .iso8601)))
            }
            weekOfYear += 2
        }
        return  intervals
    }
}