Julian is an Apple Watch complication app. It's sole purpose it to provide the Julian date as quick as possible.
By using Julian with an Apple Watch you'll always have current Julian date at a wrists flick away. Even if not using the app paired with an Apple Watch, Julian will still provide the latest Julian date in two ways.
If you choose to allow Julian notification permission it will display a notification badge with the current Julian date as the notification count. No alerts will be presented or noises made, the badge will simply autoupdate at midnight.
Another way Julian will give you the latest date is by opening the app. Due to it's simplicity Julian launches extremely quickly and displays three Julian date formats for convenience.