@swift-5.1.5
import Foundation let iso8601WithFractionalSecondFormatter: DateFormatter = { let formatter = DateFormatter() formatter.locale = Locale(identifier: "en_US_POSIX") formatter.dateFormat = "yyyy'-'MM'-'dd'T'HH':'mm':'ss.SSSSSS" formatter.timeZone = TimeZone(secondsFromGMT: 0) return formatter }() var d = Date(timeIntervalSinceReferenceDate: 0) for _ in 0..<10 { print(iso8601WithFractionalSecondFormatter.string(from: d)) d += 0.0001 }