This is still broken. The following code import Foundation let formatter = DateComponentsFormatter() formatter.unitsStyle = .full formatter.allowedUnits = [.year, .month, .weekOfMonth, .day, .hour] formatter.maximumUnitCount = 1 // Use the configured formatter to generate the string. for i in 0..<30 { let seconds: TimeInterval = 24.0*3600.0*(Double(i) + 0.5) print("\(Double(i) + 0.5) days = \(formatter.string(from: seconds)!)") } produces the following output. Fractional days seem to really break things. 0.5 days = 12 hours 1.5 days = 2 days 2.5 days = 3 days 3.5 days = 4 days 4.5 days = 5 days 5.5 days = 0 months 6.5 days = 0 months 7.5 days = 1 week 8.5 days = 2 weeks 9.5 days = 2 weeks 10.5 days = 2 weeks 11.5 days = 2 weeks 12.5 days = 2 weeks 13.5 days = 1 week 14.5 days = 2 weeks 15.5 days = 2 weeks 16.5 days = 2 weeks 17.5 days = 2 weeks 18.5 days = 2 weeks 19.5 days = 2 weeks 20.5 days = 2 weeks 21.5 days = 3 weeks 22.5 days = 3 weeks 23.5 days = 3 weeks 24.5 days = 3 weeks 25.5 days = 3 weeks 26.5 days = 3 weeks 27.5 days = 3 weeks 28.5 days = 4 weeks 29.5 days = 4 weeks