Kronos is an NTP client library written in Swift. It supports sub-seconds precision and provides an stable monotonic clock that won't be affected by clock changes.

Example app

This is an example app that displays the monotonic Clock.now on the left and the system clock (initially out of date) on the right.

Usage

Sync clock using a pool of NTP servers

Calling Clock.sync will fire a bunch of NTP requests to up to 5 of the servers on the given NTP pool (default is time.apple.com). As soon as we get the first response, the given closure is called but the Clock will keep trying to get a more accurate response.

Clock.sync { date, offset in
    // This is the first sync (note that this is the fastest but not the
    // most accurate run
    print(date)
}

Get an NTP sync'ed date

Clock.now is a monotonic NSDate that won't be affected by clock changes.

NSTimer.scheduledTimerWithTimeInterval(1.0, target: self,
                                       selector: #selector(Example.tick),
                                       userInfo: nil, repeats: true)

@objc func tick() {
    print(Clock.now) // Note that this clock will get more accurate as
                     // more NTP servers respond.
}

Installation

Embedded frameworks require a minimum deployment target of iOS 8 or OS X Mavericks (10.9).

CocoaPods

CocoaPods is a dependency manager for Cocoa projects. You can install it with the following command:

$ gem install cocoapods

CocoaPods 0.39.0+ is required to build Kronos.

To integrate Kronos into your Xcode project using CocoaPods, specify it in your Podfile:

platform :ios, '8.0'
use_frameworks!

pod 'Kronos'

Then, run the following command:

$ pod install

Swift package manager (experimental)

Swift PM is a tool for managing distribution of source code.

To integrate Kronos into your project using Swift PM use:

$ export SWIFT_EXEC=/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swiftc
$ swift build

License

Kronos is maintained by Lyft and released under the Apache 2.0 license. See LICENSE for details.