Day One is available for iOS (iPhone, iPad, iPad Mini, and iPod Touch) and Mac devices. If you wish to use both the mobile and Mac versions of Day One, you have to make two separate purchases. As these versions are sold by separate stores owned and operated by Apple, Inc., you are required to individually purchase the Mac and iOS apps from those respective stores. Apple does not provide a mechanism to bundle apps in their two separate stores.
In the future, if Apple provides the ability to offer bundle pricing for iOS and Mac apps, we will consider such an offer. In the meantime, we have priced the Mac app considerably lower than its major competitors on the Mac platform.
To run Day One on more than one desktop or laptop computer, you only need to purchase it once, as is the case for any app in the Mac app store. Just open the App Store on your Mac, click on “Purchased” and you can install Day One on several computers. Of course, to do this, you will have to be logged into the same account from which you made the original purchase.
Similar to the Mac app, you can install Day One for iOS on more than one mobile device. For example, if you have an iPhone and an iPad, you only need to purchase the mobile app once, then you can install on both of those devices.