12Calendar is an iPhone application designed to enhance the convenience of checking calendars by allowing users to customize and display wallpaper calendars on their screen lock. The app offers a variety of features to tailor the calendar layout to individual preferences.

Users can choose from 24 regular layouts and 1 free layout, ranging from 1 to 12 months display options. Customization options include selecting the start day of the week, changing font styles, adjusting font sizes, modifying colors for different elements, and altering background transparency. Additionally, users can add holiday data manually or import it from the iOS calendar to avoid manual input.

Moreover, users can easily display their customized calendar on the lock screen by making adjustments within the app, providing a seamless way to access calendar information at a glance.